Quickly find the stuff you care about

Beagle is a GNOME 2 application which implements a search tool that ransacks your personal information space to find whatever you’re looking for: documents, emails. web history, IM/IRC conversations, source code, images, music files, applications etc. Beagle is written on C# and based on Mono and GTK#.
Google has released a Google Desktop Search which is the similar to Beagle but it works only under Windows.