Our pals at Engadget know cables and hacks. And those are two great tastes that taste great together; Engadget shows how to make an Xbox 360 VGA cable out of a lowly composite part.
Unlike the PS2 and GameCube, the Xbox 360 cables include every pin -- even the ones not used by the cable-specific video connection. Because these pins already connect to the console, it's just a matter of wiring a VGA socket to the previously-unused terminals.
Total cost? $7. Get out the soldering iron, and save your money for games.
See also: PSA: Use the right cables for your TV