Carl, I'm not sure what type of card your 350D uses, but I've successfully used Kingston C/F cards on my 20D, 50D and 5DII without any problems. I bought 16Gb Kingston cards from
shoppingsquare for under $60 each. They have a transfer rate of 15Mb/s which is as good as the UltraII spec. The speed of the card shouldn't be a factor anyway, slower transfer speeds simply mean the camera can't write to the card as quickly and burst (continuous frame) rates are the only thing that should be affected. Don't be tempted to buy from ebay, many ebay sellers are selling knock offs which are sub standard.