I have a single memorized passphrase and generate a new password for each site by hashing it with the hostname. This bookmarklet asks for the passphrase, grabs the hostname from the current URL, MD5s them, and inserts the first 8 characters of the result into each password field on the current page. It's all done locally in Javascript so nothing secret is passed across the 'net which makes it secure except for shoulder-surfers and keyloggers - good enough for most stuff. And it has the great advantage that there's no locked file of passwords to lose.