I just visited the Delta Airlines website to check my milage, and they've completely redone the SkyMiles Online Service Center.

New features include:

Ability to track usage of 800-mile segment upgrades (shows when you used and earned them)

Ability to purchase 800-mile segment upgrades with either money or miles

Ability to redeem SkyMiles for awards

Online membership guide, including Medallion membership guide (they did not have the Medallion level membership guide online previously as far as I know).

This is in addition to other enhancements they added recently, such as the ability to change your address and request replacement cards.

Also, this includes Delta's much touted (at least by me!) up to the minute milage tracking!

Also, it looks like Delta is changing the design on all of their frequent flyer membership cards!