If you haven't tried it yet, Trillian for BlackBerry is now in another beta stage with version 18.104.22.168. Similar to other multiple IM client apps, Trillian lets you connect to multiple IM and social networks at the same time. Some of the IM's you can connect to are Astra, AIM, Yahoo, ICQ, MSN, MySpaceIM, Google Talk, Jabber and Facebook and they are continuing to update with more. While some multiple IM clients are going for upwards of $30.00, Trillian can be had for only $4.99. Its a great price and they are constantly making improvements!
Before this latest beta release 22.214.171.124, it was limited to portrait only on the Blackberry Storm 1 and 2. Now this current time limited beta allows for both portrait AND landscape mode, which the latter I prefer. I was also pleasantly surprised to see Inbox integration. I am sure there are other improvements as well but have yet to find them.
If you are using Trillian for BlackBerry, and have upgraded to the time limited version 126.96.36.199, let us know what else you have found!