BeeJive.com has released their web based instant messanging client for the iPhone at iphone.beejive.com.
JiveTalk for iPhone is currently available to the public as an open alpha, and free to use. Because this is an alpha release, you may experience some problems/defects. Please report these to firstname.lastname@example.org. Thank you for choosing JiveTalk!
Overall expereience with the iPhone designed client has been very positive. JiveTalk allows you to connect to multiple instant messaging networks simultaneously, including AIM (iChat), Google Talk, ICQ, Jabber, MSN Messenger and Yahoo Messenger.