Normally I wouldn't recommend buying directly from a manufacturer's Web site unless that was the only way to buy a product. However, it looks like "Cyber Monday" may be an exception to that rule--at least in the case of SanDisk, which is offering some significant discounts on its flash memory.
For example, an 8GB Ultra II SDHC card that regularly goes for $49.99 is cut to $20.99. The price of a 4GB Memory Stick Pro Duo is cut in half, down to $19.99.
If you take more pictures with your phone than your camera, you might want to grab an 8GB microSDHC card for $29.99 (down from $69.99). Other card types and sizes are on sale, too.
The discounts end today, though, at 11:59 p.m. PT and are in limited quantities.