Update two or more repositories...

gistfile1.txt

#I update github and gitorious (mi principal trunk is in gitorious)

# w/GitHub
git remote add github git@github.com:username/project.git

# w/Gitorious
git remote add gitorious git@gitorious.org:username/project.git

# and updating

git push gitorious master
git push github master 

# Another option is use .git/config file:
[core]
        repositoryformatversion = 0
        filemode = true
        bare = false
        ignorecase = true
        logallrefupdates = true
        autocrlf = false
[user]
        name = User Name
        email = username@mail.com
[remote "gitorious"]
        url = git@gitorious.org:project/mainline.git
        fetch = +refs/heads/*:refs/remotes/origin/*
[remote "github"]
        url = git@github.com:username/project.git
        fetch = +refs/heads/*:refs/remotes/github/*
[remote "public"]
        url = git@github.com:username/monopse.git
        url = git@gitorious.org:monopse/mainline.git

#and then, sync using command: git push public and voila!

#cheers!