I have just bought a 2GB SD (Kingston) from Ebay for c. £10.
Re speed, there are conflicting views on this. My feeling is that for cameras it makes no real difference. I did a test on my HP4700 PDA once between a standard cheap one, and a very expensive Kingston "high speed" one which had some sort of extra fast interface mode. There was about a 2x difference on a big file transfer, but this was not visible on a camera. The price difference was about 5x.
It is the 4GB cards that are not compatible with many devices. I have one here; it works in the LS800 tablet computer but does not work in any of several cameras, even a 1 year old Pentax DL.