First there was the Google Desktop Search beta. I installed it and then after 2 weeks uninstalled it.
Now there is a new one from Microsoft named the MSN Toolbar Suite in beta.
I really like the MSN Toolbar Suite so far, but it will take 2 weeks to know for sure. I can search everything on my hard drive, email, and the web from one convenient location. I also have not noticed the web linking/mixing or caching encrypted data like the Google tool which concerned me.
I have read that Yahoo has a desktop search tool on target for January 2005.