Many hash iterations: append salt every time?

Question

I have used unsalted md5/sha1 for long time, but as this method isn\'t really secure (and is getting even less secure as time goes by) I decided to switch to a salted sha512

Answer 1

I prefer to go with a double sha1 with two different salts and prevent DoS delaying the answer incrementally (with a simple usleep) for every invalid password check.