Google Desktop gives you easy access to information on your computer and from the web.

It's a desktop search application that provides full text search over your email, computer files, music, photos, chats and web pages that you've viewed. By making your computer searchable, Google Desktop puts your information easily within your reach and frees you from having to manually organize your files, emails and bookmarks. It makes searching your computer as easy as searching the web with Google.

With Google Desktop you can search:

Email from Gmail, Outlook 2000+, Outlook Express 5+, Netscape Mail 7.1+, Mozilla Mail 1.4+ and Thunderbird.
Files on your computer, including text, Word, Excel, Powerpoint, PDF, MP3, image, audio, and video files. You can even search your media files by meta-tag: for instance, by artist name and song title, not just the file name.
Web pages you've viewed using Internet Explorer 5+, Netscape 7.1+, Mozilla 1.4+ and Firefox.
Chats from AOL 7+, AOL Instant Messenger 5+, and MSN Messenger.

With Sidebar you can see:

Email inbox
Personalized News
Weather
Stocks
Web clips (RSS/Atom feeds)
Photos
A scratch pad for jotting down notes
Commonly used web pages and documents