From the looks of it, another feature that's beginning to pick up momentum on Apple's iPhone is instant messaging.

Developer Shaun has recently announced the release of MobileChat v2.1, the latest build of a lightweight AIM (AOL Instant Messaging) Application for the iPhone.

Aside from support for AIM accounts, MobileChat also reportedly comes packed with the following functions:

• IM Abilities
• Full Buddylist with Statuses
• Change status: Away & Online
• Suspend and stay online
• Sound notifications
• Popup Notifications
  

• Horizontal/Landscape Orientation Availability
• “New IM” finally works
• “Send” Button has been relocated to the keyboard (in place of return)
• iPhone Firmware 1.1.3 Compatibility
• DNS Issue that plagued 1.x and 2.0 has been resolved.
• BSD Subsystem dependency should be gone.
• Added support for XMPP
• GTalk has been temporarily removed
• Sign On progress notifications (as seen in screenshots)
• Disconnect Notification: if you get kicked off, or you can’t sign on, you’ll be alerted now
• Conversation code-base optimized