You can win a pair of 8800GS SLi cards over at Motherboards.org just for filling out their contest form. Two XFX GeForce 8800 GS 384MB DDR3 XXX cards, to be precise.

Or, if you're more in the market for a shiny new case, you could win an NZXT Tempest over at OCIA. This is the case that really resembles Antec's 900 - plenty of blue fans and airflow. This contest is forums-based; you need to be a member, & post a pic of your case or work area, and the crappiest submission wins. Hah.