From what I understand rainbow tables are not really used anymore -- they were useful when it took longer to calculate hashes, but nowadays you just need a decent graphics card to calculate a few billion hashes (MD5 or SHA1) PER SECOND.

Per-hash salts don't really slow that down at all, unfortunately.

Short-version: don't use the hash algorithms that are designed to be fast for protecting sensitive data; use something solid with a work factor instead.