Oh I absolutely agree on the importance of several passwords. I really don't like these centralized authentication systems or password keepers. It may be the height of paranoia, but if I'm going to the trouble of making up all these multiple strong passwords, why would I then put them all in one location? That's one system to compromise to get the keys to all my accounts.
Really the issue is the inability to remember multiple passwords for the average person (or the inability to want to remember them). I like the idea of using a custom, human operable hash function to generate passwords. Take this site as an example, the input would be slashdot (the domain), you take that as the seed and apply some sort of algorithm/hashing function in your head to create the password. It needs to be complex enough to not just be "add '123' to the end", but simple enough to do while sitting at a keyboard. If you can still recognize the domain in the output it's a failure. The beauty of it is that you never need to remember your passwords, just the algorithm. If you want to log in to a site, you look at the domain and apply your hashing algo to 'remember' your password. If you want to change the passwords, change your algorithm. This is of course far beyond the level of the average user, but it avoids putting all your keys in one box.