I'm pretty sure the entire title of DDR RAM is "PC3200 DDR SDRAM." That's what I've seen all over the place, anyway. DDR RAM is a type of SDRAM. Actually, to make it less confusing, DDR RAM and DDR SDRAM are the same thing.
*edit* I don't want to go too complex with this, but DDR RAM isn't just SDRAM; it's DDR SDRAM. Calling it SDRAM only is wrong.
*edit again* <A HREF=http://www.ddrsdrammemory.com/>This explains it pretty damn good</A>.
-Lasereth