Napster for AOL's Instant Messenger
At AIMster you can download software that allows you to exchange files with other users, similar to Napster. Because the program uses the AOL Instant Messenger's buddy lists, data is only exchanged between people who know each other.
However, there are still some problems with the software, so you can sometimes not even use it contact other users or exchange data even though they are verifiably online. So it will take some time until the hopefully error-free version 1.0 appears. We are currently at version 0.36.