One of the very best IM app on the iPhone. It is one of the very best at supporting pretty much every IM service from AIM, Google Talk, Facebook, Yahoo, MSN—it and IMChat/Jabber. The UI on the iPhone is fantastic and very clean with neat gestures like swiping to switch between conversations. Meebo also has a slick preview of your chats in the buddy list view. There's also a searchable chat history on your phone or through Meebo.com and great push notifications too. The only thing that sucks about Meebo is there isn't an iPad version but if you're looking for an IM app through and through, start with Meebo. The distracting bells and whistles of other IM apps.

It's one of my favorite IM apps on the iPhone and my go to IM app for the iPad. Imo supports all the IM protocols that a normal person would use (AIM, Google Talk, Facebook, etc.) and handles your chats in a nice tabbed interface that's dead easy to navigate. You can send picture IMs, attach videos and even send voice IMs (like a walkie talkie of sorts). Push notifications work for 72 hours after you close the app and there's a fully searchable chat history. It's polished, light, and quick.

A seriously excellent IM app that elegantly uses the small space of an iPhone to its advantage. No other IM app is nearly as creative, Beejive's transparent overlay text bubble doesn't typically fit within the iPhone's UI but it works—you can see the conversation while typing without losing the flow of YOUR message. Beejive also throws in push notifications for SEVEN days and supports the usual slew of protocols. If price was no object, I'd rate it the best IM app on the iPhone but it costs 10 bucks on the iPhone and 10 bucks on the iPad