Performance parts
POWERDYNE SUPERCHARGERS better prices than Vortech
Borla I have found that Borla exhaust sounds better than flowmasters. But it's all personal preferance.
Crutchfield Pretty decent prices on the Audio equipment.
Billet Specialties Makes things look good... and that's what we all like

Here's some just plain ole GO FAST parts...
Hypertech Programmers
Truck Performance This has information on not only our X's but on most all trucks
K&N Filters Link for the K&N generation 2 filter system
GM Goodwrench
Xtreme Owners.com
S-SeriesForum.com