In the tradition of making our favorite chat program easy to migrate to, we can now import Proteus and Fire logs.
There is a php script to import fire logs (which are just HTML, and AIGhettoHTMLDecoder can handle them just fine) and a perl script to import Proteus logs. Both can be found in the Utilities folder of hte Adium source.
The Proteus one will be able to import MSN and such soon.
There are directions on how to run the scripts in the scripts themselves.