Translation teams already exist for many languages.
You can browse for teams and
languages on Damned Lies,
the Web application used for tracking translation status of GNOME.
To join a team, contact the team leader.
If a team does not exist for your language, consider starting one.
If no team for your language is listed on the pages linked above and you want to start a new one,
please send an email to announce the new team
to the mailing list.
It should have a subject like "New team for [your language name] ([your language code])"
and contain the name and the email of the person who is the new coordinator for that language
(And if one exists, the URL of the Team's page).
(The webmaster will add this team to the relevant pages shortly after)
For more details, look at starting a new team in Gnome Wiki.
We would like to encourage translation teams to have web pages, even if they are simple ones, and mailing lists. For many teams, the easiest and best way to do this is to use Savannah. Savannah will allow you to create a project for your team, providing you use it to advance open source development, which you are doing. It will give you a place to set up web pages, have a mailing list, and place files for people to download. You can even set up CVS if you find that helpful. It also allows you to give access to multiple team members so you can each update the web pages, downloadable files, etc.
If there are any errors in the contact/web address of a team please write to the mailing list.