Spintastics Skill Toys, Inc.
Sells the Technic, Tornado, Tigershark, Torch and other brands.
http://www.spintastics.com/

Atomic Toy Mills
Hand assembled yo-yos.
http://www.atomictoymills.com/

YO-topia Toys
Lunastix, beamO, yoyos, hyromids, tops, and jump ropes.
http://www.yotopia.com

Yo Yo Universe
By Mackinaw Kite Company. Sales and contests.
http://yoyouniverse.com/

Yoyoplay.com
Yoyos from Spintastics, Team Losi, Yomega, Yoyojam and others.
http://yoyoplay.com/

TheYoStore.com
Name brands and the latest models.
http://theyostore.com

Yo-Yo Store
Large collection of yo-yos, books and accessories.
http://www.yoyostore.com/

Premium Hardwood Yo-yos
Offering wooden yo-yos in multiple shapes and with fixed or trans axles.
http://home.flash.net/~tleo/

Infinite Illusions
Specializing in yo-yos and accessories. Also offering apparel, books and DVD, and juggling.
http://www.yoyoguy.com/