Best voip clients

So you want to use voip and you dont want to download one of the basic clients each provider offers. That is a very wise decision because you will be changing provider very often and to keep feeling your computer with ultiple clients is not a good solution. Furthermore most of the Voip SIP clients in the market are free as well and offer several additional features. Lets have a look at the contenders:

Ekiga:

Ekiga (formely known as GnomeMeeting) is an open source VoIP and video conferencing application for GNOME. Ekiga uses both the H.323 and SIP protocols. It supports many audio and video codecs, and is interoperable with other SIP compliant software and also with Microsoft NetMeeting.
To get started: Download Ekiga for your distribution and get a free SIP-Address at ekiga.net.

Features:

SIP compliant
Registrar support
Possibility to simultaneously register to several accounts
Proxy support
Outbound Proxy support
Call Hold
Call Transfer
Call Forwarding on no answer, on busy, always
Configurable port ranges
Instant Messaging
RFC2833 DTMFs support
Message Waiting Indications Support
ENUM support
Transparent NAT Support using STUN
SIP re-INVITE support
SIP/SIMPLE Presence support
Line Monitoring
Extended presence publishing
Full SIP capabilities exchange for codecs
SIP INFO DTMF support
Ability to simultaneously handle several network interfaces

Runs on:

Linux and windows platforms

SIP Communicator:

SIP Communicator is an audio/video Internet phone and instant messenger that supports some of the most popular instant messaging and telephony protocols such as SIP, Jabber, AIM/ICQ, MSN, Yahoo! Messenger, Bonjour, IRC, RSS and counting.

SIP Communicator is completely Open Source / Free Software, and is freely available under the terms of the GNU Lesser General Public License.

Features:

Runs on:

Linux, mac and windows platforms

Twinkle:

Twinkle is, as I mentioned above, an SIP program. SIP is a protocol for voice-over-internet-protocol (VoIP). Basically, it enables users to call each other using only their computers and a microphone. It’s also an open protocol; so, unlike a closed protocol like Skype, you can use any program that supports SIP rather than being tied to a specific client.

Since Twinkle is a popular program, it’s already in most of the repositories out there. Debian and Ubuntu users can install the twinkle package in their repositories, while openSuSE users have Twinkle pre-installed in the DVD version. You can also compile Twinkle from source, though you’ll need Qt’s headers and a few other libraries (don’t use Qt 4.4, use 3.3.0 or later). See the Twinkle homepage for more information.

Features

In addition to making basic voice calls Twinkle provides you the following features:

2 call appearances (lines)
Multiple active call identities
Custom ring tones
Call Waiting
Call Hold
3-way conference calling
Mute
Call redirection on demand
Call redirection unconditional
Call redirection when busy
Call redirection no answer
Reject call redirection request
Blind call transfer
Call transfer with consultation (attended call transfer)
Reject call transfer request
Call reject
Repeat last call
Do not disturb
Auto answer
Message Waiting Inidication
Voice mail speed dial
User defineable scripts triggered on call events
E.g. to implement selective call reject or distinctive ringing
RFC 2833 DTMF events
Inband DTMF
Out-of-band DTMF (SIP INFO)
STUN support for NAT traversal
Send NAT keep alive packets when using STUN
NAT traversal through static provisioning
Persistent TCP connections for NAT traversal
Missed call indication
History of call detail records for incoming, outgoing, successful and missed calls
DNS SRV support
Automatic failover to an alternate server if a server is unavailable
Other programs can originate a SIP call via Twinkle, e.g. call from address book
System tray icon
System tray menu to quickly originate and answer calls while Twinkle stays hidden
User defineable number conversion rules
Simple address book
Support for UDP and TCP as transport for SIP
Presence
Instant messaging
Simple file transfer with instant message
Instant message composition indication
Command line interface (CLI)

Runs on:

Linux platforms

Empathy

Empathy is a messaging program which supports text, voice, and video chat and file transfers over many different protocols. You can tell it about your accounts on all those services and do all your chatting within one application.

Empathy uses Telepathy for protocol support and has a user interface based on Gossip. Empathy is the default chat client in current versions of GNOME, making it easier for other GNOME applications to integrate collaboration functionality using Telepathy.

Features:

Multi-protocol: Google Talk (Jabber/XMPP), MSN, IRC, Salut, AIM, Facebook, Yahoo!, Gadu Gadu, Groupwise, ICQ and QQ. (Supported protocols depend on installed Telepathy Connection Manager components.) Supports all protocols supported by Pidgin.
File transfer for XMPP, and local networks.
Voice and video call using SIP, XMPP, Google Talk and MSN.
Some IRC support.
For detailed list of supported protocol features see here
Conversation theming (see list of supported Adium themes).
Sharing and viewing location information.
Private and group chat (with smileys and spell checking).
Conversation logging.
Automatic away and extended away presence.
Automatic reconnection using Network Manager.
Python bindings for libempathy and libempathy-gtk
Support for collaborative applications (“tubes”).

Runs on:

Linux platforms

Fring:

fring™ is a mobile internet community and communication service that allows friends to connect, share experiences and enhance their online communities together.

Using your handset′s internet connection, you can interact with friends on all your favourite social networks including Skype®, MSN Messenger®, Google Talk™, ICQ, SIP, Twitter, Yahoo!™ and AIM®. You can listen to music with your Last.fm friends, check out what each other are up to on Facebook, receive alerts of new Google Mail™ and tailor make your very own fring by adding more cool experiences from fringAdd-ons™.

fring puts all your online friends into one, dynamic fringFriends™ buddy list, which is always connected so you can enjoy free calls and instant messaging with all your online friends, see their real-time status, and even find each other’s actual location.

fring combines your multiple IM contacts into one dynamic profile, which shows each friend’s current availability at a quick glance and enables interaction, all directly from this combined mobile profile.

fring makes your mobile the ultimate social device.

As well as it′s social appeal, fring also lets you make affordable local and international calls & live video calls to landline and regular cellular numbers using your SkypeOut/SkypeIn account or almost any internet voice service (SIP) such as a1 overIP, PlusNet, Eutelia, Net2Phone and others; even from non-SIP enabled handsets.

What′s more, fring does all the work for you, automatically logging you into your favorite WiFi hotspots so you save time and hassle without having to configure your WiFi access points each time.

As easy to download as a ringtone and simple to install and use, fring is PC-independent and does not require any dedicated hardware. All you need to use fring is a supported handset with internet connectivity and an internet data package or WiFi access.
.

Features:

Mobile VoIP communication[6]
Interconnects with PC VoIP applications,[7] including Skype, Windows Live Messenger, ICQ, Google Talk, Yahoo! and AIM.[8]
Live chat between Skype, Windows Live Messenger, ICQ, Google Talk, Yahoo Messenger, AIM and Twitter[9]
PSTN and GSM lines using SkypeOut or SIP termination
Send & Receive files[10] between Skype, Windows Live Messenger, Yahoo Messenger and fring[11]
Real time presence indication
Call History[12]
Auto-roam[13] in and out of WiFi hotspots[

Runs on:

Linux, Java ME, Symbian OS, Windows Mobile and iPhone

Gizmo5

Does the world really need another VoIP client? Here's one Gizmo that thinks so.

Gizmo5's interface is compact and rectangular, with tabs on the top just below the Menu bar and a series of ancillary commands like Chat and Add Contact available at the bottom. There are very few differences between Gizmo's design and its biggest competitor's, and a little originality could've gone a long way here.

Also similar to Skype, Gizmo provides free VoIP for computer-to-computer voice chatting as well as text chatting. It also allows for computer-to-telephone voice chatting for both mobile phones and landlines. It has one feature that Skype lacks: it lets you conference call with multiple PCs by entering in a random, shared number. Overall, the sound clarity and quality was excellent, with no lagging nor echoing. Gizmo also says it provides asymmetrical chat-client VoIP, so you can use Gizmo and your headset to talk to somebody on Windows Live or Google Talk. We couldn't get that feature to work, but it's a smart idea and we hope it gets debugged soon.

Overall, Gizmo's got some good stuff and some room for improvement. If you despise Skype or are just interested in alternatives, you might want to give this one a try, but otherwise we'd recommend holding off.

Features:

Support: Online
Guarantee: N/A
Residential Plan: Yes
Small Business Plan: Yes
411 Service: Yes
911 Service: No Call Return (*69): N/A
Call Waiting: No
Caller ID: Limited
Click-to-Call: Yes
Fax Line (FoIP): Available
International Calling: Yes
IP PBX Solution: Yes
Keep Your Number: No
PC-to-PC Calling: Yes
PC-to-Phone Calling: Yes
Virtual Phone Numbers: No

Runs on:

Linux, Mac and Windows platforms