'Cypherpunk' and 'cypherpunks' are generic usernames that can be used for many sites, allowing you to log in and use the site without going through all the rigmarole of signing up for your own account. It is akin to the everyone account on E2 (which has now been opened up to level one users without logging into the account).
Cypherpunk accounts should use the same password as username. There are some sites that don't allow this, and there are a few things you can try. First, if you are logging in with 'cypherpunk', try 'cypherpunks' as the password (and vice versa). If this doesn't work, you are probably screwed, but you can try 'secret', 'writecode', or 'punkcypher'. If these don't work, cypherpunks (and cypherpunk, too) has a Mailinator account (http://www.mailinator.com); you can try having the site send your "forgotten password" to cypherpunks@mailinator.com. No password is needed to read your Mailinator messages.
Many sites have cypherpunks accounts, including Hotmail, Facebook, and Digg. Gmail has one, but someone has borked it up good, and Gmail requires a security question to request the password. If you can get in, please fix it!
If a site doesn't have a cypherpunks account, and you find that you have reason to sign up for the site's services, consider signing up as cypherpunks. If you like the site, you can always set up your own account later.
You never know what you'll find; Yahoo, along with chypherpunks, cypherpunk, and cypherpunkz, also has a siferpunkz account. It has the password of writecode. I haven't been able to find the password to any of the other Yahoo accounts. I believe that they are actually blocked from being accounts, as mail sent to them is not delivered.