Just select some text (or just have the cursor on the word you wish to search for) and press Ctrl+F3.  Ctrl+Shift+F3 will do a reverse search.

Note that a Ctrl+F3 search uses the following options: 

• is case sensitive
• searches hidden text
• allows for partial matching
• does not use regular expressions

Technorati tags: VS2005Tip, VS2008Tip