Lots of sites I don't want to forget about!
Bear Tooth Woods - ordered my pen squaring jig from them plus some crushed stone for inlay work. They also have good special prices on some wood blanks.
Craft Supplies USA - Lots of tools, blanks, kits.
Rockler Woodworking & Hardware - Where I first picked up the woodturning bug. Have taken several classes from Pete at the Pasadena Store. Have also done some shopping at the Ontario store now managed by Cory. The guys at both stores are great.
TurnTex Woodworks: Ordered stabilizing chamber, cactus juice (resin), and wood dyes.
Woodcraft - They have a store in Stanton (moving to Fountain Valley in Oct/Nov). Taking a class on the band saw in December!
WoodworkingTalk.com - A woodworker's forum with one group just for woodturners.
The Pen Shop - A forum that is not very active but has a few good tutorials.