Dan Appleman did a talk at VSLive Orlando about "Discoverability". I was not able to attend the session but my co-worker did.
I also heard Dan talk on the internet talk show .Net Rocks regarding the same topic. One interesting link that was served up was a site that uses a google custom search. Dan has set one up for only search the top .NET sites. The site is www.searchdotnet.com and currently searchs about 300 sites. Some of those sites are the MSDN blog sites so the actual depth of the content being searched is much greater than the 300 sites.
So far it has been returning much more relative results than straight google searchs on .NET topics.