If you use Trillian as your IM consolidation tool (connect to Yahoo IM, ICQ, AIM and MSN Messenger) - you'll want to update due to a recently found security hole. The current, patched version is 3.10.0, 18 May 2008. Even though the 'Check for Update' in Trillian doesn't say you need an update, if your Help/About doesn't have the 18 May 2008 date on it, you'll want to manually update your software from Trillian's website.
If you don't use Trillian for IM, it's worth investigating. If you use basic IM clients (not the voice and webcam sharing capabilities, which Trillian doesn't replicate) and have friends on more than one network, it will help you organize your friends, and allow you to run just one IM client. Additionally, it offers encryption compatible with several services and allows connectivity to IRC as well.