AIM

I wasn't sure where to post this so i decided general discussion was good enough. i'm using OSX 10.3.7 I was wondering if anyone knew of some plugins or AIM clones that keep up with all the features of the windows version of AIM. one thing i'd like especially is being able to be invisible. it's rediculous, Windows is up to like 5.9 and we're stuck at 4.7