Hidden Features of Visual Studio (2005-2010)?

Make a selection with ALT pressed - selects a square of text instead of whole lines.

Tracepoints!

Put a breakpoint on a line of code. Bring up the Breakpoints Window and right click on the new breakpoint. Select 'When Hit...'. By ticking the 'Print a message' check box Visual Studio will print out a message to the Debug Output every time the line of code is executed, rather than (or as well as) breaking on it. You can also get it to execute a macro as it passes the line.

You can drag code to the ToolBox. Try it!

Click an identifier (class name, variable, etc) then hit F12 for "Go To Definition". I'm always amazed how many people I watch code use the slower right-click -> "Go To Definition" method.

EDIT: Then you can use Ctrl+- to jump back to where you were.