Mike Ormond has links to some Windows Sidebar gadgets for searching MSDN. Both Tim Heuer and Nikhil seem to have been looking at this.
I’ll be doing a grok talk on Windows Sidebar gadget development at the London .NET user group Office and Vista Launch event.
BTW Mike is running the London Marathon for Hearing Dogs for the Deaf and you can sponsor him from the link on his page. Go on, if only for the chance to see Mike run.