Enabling SSH login to all my Github repositories

I have 33 repositories on Github. Recently I made a ssh key and uploaded the public key to Github.
So far so good.
I found out that I had to give the git command:

git remote set-url origin git@github.com:username/your-repository.git to enable logging in to a particular repository.

But isn't there an easier way than this command?
Is it possible to configure .ssh/config/ in such a way that I can login to all Github repo's without having to type that line for all repositories individually?
Or a script that would make that possible?

http://dt.iki.fi/migrating-git-repos
should also work the other way round.