I really like the password generator, built into Apple's keychain and System preferences. Passwords are secure and memorable. Only problem is that accessing it takes many steps. Running it from the command line would be much faster.
Now there seems to be a reverse-engineered library for this. It's even linked into Homebrew. To install it just run:
brew install sf-pwgen
Then you can generate passwords like this:
seek5(mails folks5:gores agism6_betty bak6}damsons lingo4/altos