The sim card slot should work if you have a Smartbook with a 3G modem installed. otherwise it isn't connected to anything.
I don't have any SD cards larger than 4GB at the moment but I would guess most SDHC cards will work fine in the left hand slot. the rear slot (MicroSD) however is a bit of a problem. some cards work and some don't (I think because of the voltage being a bit lower than most cards expect in that slot, and possibly other reasons, some searching around in the forums should get you a better detailed explanation from Matt. )
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Genesi USA, Inc.