On iPhone 1.1.4 we used to enjoy Agile Messenger via Installer. But here in V2.0 a free App Store application IM+ All-In-One-Messenger works just fine. Though the features are not as many as the Agile Messenger, its still enough.
IM+ missed out on Photo Transfer, Smileys etc! All in all a basic messenger that supports Gtalk, Yahoo IM, MSN, ICQ, Jabber, MySpace & AOL! Video Downstairs
Video also on YouTube
An official and FREE Appstore Application – Tested on iPhone firmware version 2.0.2