http://themes.wordpress.net (not .org)
You can also add it to the list in the Codex.
Damn, it won’t let me create an account to upload my theme.
Yeah, I went there but when I go to create and account it says “User registration is currently not allowed.”
On that page I don’t see anything about creating an account but you may be right. I never uploaded a theme there…
Or, it maybe they stopped allowing people to upload new themes for while – lately too much garbage (read: sponsored themes) has been uploaded, it was time to stop it.
