Good choice for a lightweight checksum algorithm?

Question

I find myself needing to generate a checksum for a string of data, for consistency purposes. The broad idea is that the client can regenerate the checksum based on the payl

Answer 1

[UPDATE 30/5/2013: The link to the old JS CRC32 implementation died, so I've now linked to a different one.]

Google CRC32: fast, and much lighter weight than MD5 et al. There is a Javascript implementation here.