pw

This is not the easiest way off having secure passwords that you don't have to store. Yes, there are password managers but if you don't want to store/save your passwords anywhere you could use pwdhash which is based off MD5. Friend of mine actually built one off SHA1 and it's all open at https://github.com/simontabor/pw/ or www.pwapp.io. It's 40 chars so much much better than pwdhash (but that's the original I guess).

Probably didn't make it clear enough, it's repeatable so you'd use Twitter as the service and whatever password you usually use (master password), it'd come back with a hash and you use that as your Twitter password. Whenever you need your Twitter password, you repeat the process. https://github.com/simontabor/pw - it's got node-webkit so there's a mac app in that repo and should also work on Windows + Linux nicely (this is simply to take it out of the browser where it's easy to lose tabs and put it in a clean, small window)