For doing multi Chat Adium X is one of the best I have used on both the PC or Mac. I also like Proteus but it costs where Adium X is free. Also I have had better luck with Adium X and Direct Connects than with Proteus. Since I do a lot of Transfering Pics with friends in different states, Adium X did it for me. If you are just using AIM then IChat works great but if you need Yahoo, MSN, ICQ ETC. Adium X is hard to beat. There is also another multi chat client called Fire. I know it works very well.