The new beta of Google Desktop (you can
download it here) includes an API that lets developers create plug-ins. In addition to indexing AIM chats, there are now plug-ins for Miranda, Trillian, Gaim and even mIRC.
I've been using version 1 for months, and it's the fastest way to search for stuff on my HD -- 100x faster than Start > Search; faster than searching through emails in Microsoft Outlook; faster than anything else I've used for that matter.
I'm downloading version 2 now...
Screenshot:
It's interesting... I worked for a dot-com back in the late '90s that built a similar toolbar. It was extensible and allowed personalization. You could display stock tickers, weather, etc. Sadly, our IPO never happened. Maybe we were ahead of our time.