Not sure if this topic has been beat down to ground, but I've been told by the folks at Best Buys that the Nokia 6620 should be able to use SD Cards sinc SD and MMC are compatible. I didn't quite believe the statement so I wanna check here first....
SD Cards for 6620
The Best Buys folks you talked to do not have all the facts straight.
A device that takes SD cards can also take MMC cards, but vice versa is not true.
The 6620 can only take MMC cards.