I bought a 20x 512mb MMC on E-bay for my Nokia 6230 which arrived from the States in 5 days. Only cost me £31 (incl. P&P) which I thought was an excellent price and you can purchase them up to 1GB in size.
The card is very small but is accessed quite quickly by the phone... you can purchase faster 60x cards if you need the extra speed however I think the camera has to be able to access the card at that speed to get the full benefit?
I have a 256mb Compact Flash card on my Canon Ixus V3 which serves me well but for the small price of the 512mb card if I was buying again that's the size I would go for... if your new camera has video capability bear in mind the clips can take up a fair bit of storage.
A 30 second video clip (with sound) takes up approx. 20mb of space on my 256mb Compact Flash Card. To be honest when I first got my camera I didn't think I would use the video feature that much but now I use it just as much as stills!!!
I checked a couple of forums regarding MMC brand compatibility and it wasn't an issue for the Nokia and I wouldn't think it would be an issue for your camera?
Most of the UK web sites that supply the cards have compatibility charts so you can check to see if your device is listed before you buy the card. Sorry I don't have links but if you do a search in Google you'l find what you're after.