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Technically yes, but don't use md5 for anything security-related ever. It's broken. http://www.mscs.dal.ca/~selinger/md5collision/ is just one example. (I also remember reading some years ago that md5s within md5s can make the resulting hash more vulnerable to certain attacks but I don't have any formal knowledge in cryptology to say for sure.) Use bcrypt/scrypt and you're automatically protected from both rainbow tables and brute force.

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H(Salt . H(Password)) is a lot like an hmac (minus the secret part and the padding). I'm not sure about the pre-image vulnerability mentioned on wikipedia's md5 page, but as for collision vulnerabilities, according to wikipedia's hmac page, "HMACs are substantially less affected by collisions than their underlying hashing algorithms alone. Therefore, HMAC-MD5 does not suffer from the same weaknesses that have been found in MD5."

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