If you already own an iPhone or any other mobile handset that connects to the Internet, it is also possible to VoIP applications to make free or cheap calls.
Here is a list of 7 VoIP applications that can be used with your cell phone…
Skype Mobile
If your phone is supported, Skype Mobile is a great way to add Skype chatting and calls to it.
Platform/Network: Java-based application that works on 50 popular phones from Nokia, Sony Ericsson, Motorola and Samsung. Can be used on numerous cellular data networks.
Cost: Free
Features: One-to-one and Group Chat, presence settings (offline, online, do not disturb).
3 Skypephone
The 3 Skypephone is best suited for those who need a few monthly mobile minutes and wish to talk/IM to their Skype friends along the way. The pre-paid feature makes it an attractive and inexpensive option for Skype chatters in the geographies it serves.
Platform/Network: Uses a specialized handset. Currently available in the UK, Italy, Austria, Hong Kong, Australia, Ireland, Denmark and Sweden.
Cost: Around £49.99 (about $98) and can be used on a pre-paid basis. Calls cost nothing if they’re made from Skype.
Features: Free Skype-to-Skype mobile calls and the ability to conduct Skype IM conversations, all without touching your computer.
iSkoot
iSkoot is a good option for keeping in touch with your Skype contacts.
Platform/Network: Mobile handsets such as BlackBerry, Nokia, Windows Mobile and Palm OS models. Also works on GSM networks.
Cost: Based on usage. Because iSkoot is a hybrid VoIP/GSM service, it uses SMS and mobile minutes when making and receiving calls or Skype IM messages.
Features: SkypeIn and Skype-to-Skype calls, Skype IM messages.
Truphone
With its smart forwarding options, Truphone is particularly useful for international travelers. Whether you’re on Wi-Fi or just your normal GSM network, you can be reached via your Truphone number no matter where you are. For times when Wi-Fi is not available, Truphone just released Truphone Anywhere, which utilizes local gateways for outgoing calls at low per-minute charges.
Platform/Network: Nokia handsets
Cost: Incoming free calls while on the Truphone network, low per-minute rates while on a GSM network. Outgoing calls are billed at very low per minute rates.
Features: Truphone offers free calls, SMS and voice mail while logged into the Truphone network via Wi-Fi. Otherwise, Truphone forwards calls to your mobile handset and you pay a low per-minute charge.
Fring
Almost comparable to normal cell phone when using Wi-Fi connection.
Platform/Network: Nokia/Symbian handsets, Widows Mobile, iPhone (pre-release beta)
Cost: Free
Features: Allows you to make VoIP calls on any SIP network, Skype or to other Fring users. Additionally, Fring is a multi-protocol IM client that will allow you to chat with your buddies on Skype, MSN, ICQ, Google Talk, Twitter, AIM and Yahoo.
Talkonaut
Great features but this new software is still unstable.
Platform/Network: Available for Java-based phones, Symbian and Windows Mobile
Cost: Free
Features: Talkonaut offers free VoIP and IM chatting. For instant messaging, the application supports Google Talk, ICQ, AIM, and Yahoo. Talkonaut can also use SIP for VoIP calling.
Nimbuzz
Responsive and easy to use. Good quality when using VoIP from Facebook to Nimbuzz over a Wi-Fi connection.
Platform/Network: Java program, Symbian - iPhone version coming soon.
Cost: Free
Features: Allows you to engage in IM conversations and conduct VoIP calls, as well as to share media such as photos and video. Nimbuzz also allows for client-to-client calls and has widgets enabling calls to originate from Facebok and MySpace. Compatible with Skype, Google Talk, AOL Instant Messenger, Windows Live Messenger, Yahoo, MySpace, Facebook and Jabber IM networks.
Our Opinion: The Symbian application is very responsive and easy to use. A VoIP call originating from my Facebook page to Nimbuzz over a Wi-Fi connection sounded good — just as good as any call over a GSM network.
Gizmo5
Great competitor to Skype supports by many platforms including iPhone. Good VoIP call quality.
Platform/Network: Nokia Symbian handsets, BlackBerry, Windows Mobile, Nokia Tablets
Cost: Free for VoIP calls, low per-minute charge to call landlines and to SMS to mobiles.
Features: Gizmo5 allows you to conduct voice calls to other Gizmo5 users and grants IM conversations with friends on Gizmo5, MSN, AIM, Yahoo and Jabber.