Siliconera has pointed out an awesome deal. Sandisk has a coupon that allows $25 off a 512MB Sandisk PRO Duo at Circuit City, GameStop, or Best Buy.
Luckily, the cards only sell for $19.99 at Best Buy so you can print out the coupon and take it in for a free memory card.
While I have not had a chance to try this out, I will be hitting Best Buy first thing tomorrow morning and pick up one (or two, or three)
[update 1]: It appears that SanDisk has changed the coupon. Now it simply says you can buy a 512MB MemoryStick PRO Duo for as low as $19.99.[via Siliconera]