Portable instant messaging!
Adium is really one of the best freeware for instant messaging with multiple IM clients on a Mac. A version of this application called "Portable Adium" was released and what it does is it incorporates all the info necessary in the folder of the application. This lets you install the app on a thumb drive, iPod or any portable storage. The advantage of this is that you can run the application on any computer without any installation necessary and your info will always be there (contact list, transcripts, etc). You can learn more about Portable Adium or download it here on MacUpdate.