Here is a list of a few companies I have seen that offer discounts for employees:

GiftTree.com
Contact Name: Sarah Dunlap
Phone: 800-931-3620 ext 258
Email: sarah@gifttree.com
Web Address: www.gifttree.com
Discount: 10% - 15% off

Sprint
Web Address: www.evpdiscount.com
Discount: varies

Apple
Discount: I have seen 5% off for some employees.

AT&T
Web Address: http://www.wireless.att.com/businesscenter/
Discount: I have seen 15% off.

Enterprise
Discount: Corporate Class Rate

Verizon
Discount: up to 25% off

AAA
Discount: 2 months free when your purchase 12 months of service

Dell
Discount: I have seen 12% off

Barnes & Noble
Discount: 5%

American Airlines
Discount: 10%

Walt Disney World
Site: http://www.orlandovacation.com/discounts