imo is a multi-protocol IM app available for iPhone/iPod touch and iPad, that supports protocols like AIM, Yahoo! Messenger, MSN Messenger, and Google Talk. As well, it's also had support for Skype instant messaging, and has been until recently one of the few free solutions for native Skype chatting on the iPad until the recent release of Skype for iPad. Even with the release of that app, some users, such as myself, may remain with imo due to the convenience of multiple account sign-in and its push notification support for all the accounts.
However, one of the problems with the Skype support in imo has been that it's been limited to one-to-one instant message support; one of the strengths of the Skype service is that it is great for organizing large groups of people together easily for group chatting. imo has announced that their iPad app has been updated to support group chatting with Skype accounts, so now imo's app has become more feature-compatible with the official Skype offerings. No registration is required to use the app, as it supports direct login with various IM protocols. As well, it supports account linking, so logging in with one account will log in to other accounts simultaneously.
Group chat support is not the end of the list of improvements to the iPad app. Image and video support has been added; files are uploaded to imo's servers and are sent as links to other users, and other imo users will be able to see them natively in the app itself. The ability to load chat history with other users in the conversation itself is now available. Two new services are also available: Hyves and VKontakte. The update for imo is available now, and the app is free as always. There's no word on if any of these features will make their way to the iPhone/iPod touch yet, though.