Here's a useful little app I think everyone ought to have. Or at least everyone who's been around on the net long enough to have two, or three, or four different IM programs and logins.
Trillian is a free program (with an upgraded Pro version) which allows you to log into all 4 major Instant messaging systems and IRC, with only one client.
Not only does this help clean up your system tray, but you have all your contacts in one list. Helpful icons show which service that person is using. With the Pro version, you can even create 'meta-contacts', which show One icon on the contact list for a given person's many IM identities. For example, I could create one 'meta-contact' called 'Brad' which would have brad's ICQ, AIM, MSN, and Yahoo messenger identities in it. If brad logs on to any one, or all, of these services, his metacontact will show online, but only show one contact no matter how many services he's logged into.
For those of us who've been using IM since ICQ was the only game in town, this is a real breakthrough to be able to get 'back to basics' by using one program to handle all of our IM needs.
Cerulean Studios: The Creators of Trillian and Trillian Pro IM Clients