The Class 10 Lexar Platinum II SDHC cards are pretty good deals right now at B&H (the 32GB card is a great deal for $32.95). Unless you are shooting with the latest, top-notch DSLRs, these cards should keep up with your camera’s ability to write data.
Notably, the Class 10 rating, which is intended for evaluating video performance, means that these cards can handle HD video capture from all the consumer camcorders and DLSRs.
If you need more speed for burst capture on high frame rate DSLRs, check out SanDisk Extreme series, which offer a max data rate of 30MB/s.
For a more detailed explanation of SDHC card classes and speed ratings, check out my prior article on Demystifying SD Cards.