There are a lot of free messengers for the iPhone, AIM, Yahoo, Windows Messenger, Trillian, IM+, Bejive, some of them you have to pay for, but they will allow you to have full access to all the chat services in a single user interface! My favorite is IM+ and I suspect it will be iOS4 updated pretty quickly. Trillian is sort of a plan jane all in one IM program, but it will likely be months before they upgrade to iOS4.