Well, I bought a 256mb SD card from ebay for just under £60 including delivery.
http://cgi.ebay.co.uk/ws/eBayISAPI.d...category=15215
The seller is the person I bought it from. The card was delivered in 3 working days and was shipped from New York, it was sealed in packaging as new.
I've never bought anything from ebay before, only sold stuff, but for me it was a great buy and the card, which has been thoroughly used daily since it arrived about two weeks ago is fantastic. I have read on this board that some people have had issues with SanDisk cards but so far so good.
CompactFlash cards are cheaper but I have a Wi-Fi card in that slot hence going for the SD.
Good luck.