Lots of recommendations already, but I'll throw in a vote for Pass[0]. It's simple, cross-platform, and doesn't require trust in any service--although you do need to trust yourself not to lose your gnupg private key.
I've been using this too, highly recommended. Very simple and usable command-line interface, integrates with Git to share all encrypted passwords across machines.
[0] http://www.zx2c4.com/projects/password-store/