Nimbuzz allows you to make calls, chat online, exchange instant messages and send files from your phone for free.
The application pulls all your contacts together in one place, so you can exchange messages with all your friends on networks such as MSN, AIM, Yahoo! Messenger, Google Talk, Jabber, Facebook, or MySpace.
The user interface combines all of your contacts from all these various networks into one place, and you can see who is online at any time. If you want to get someone's attention, you simply 'buzz' them, and Nimbuzz will be launched on their phone.
Nimbuzz also features a service called NimbuzzOut, where you can buy credits to make international calls and greatly reduced rates. Don't forget that you'll still get charged for Internet access when using Nimbuzz, though. So, if you pay for data by the megabyte then using Nimbuzz could work out to be very costly if you're not careful.
However, if you have a flat-rate plan, Nimbuzz makes for a fun and cheap way to stay in touch with friends and family around the world.