If you are tired of waiting for 37 Signals to translate Basecamp into your language, then you can do it yourself with http://mylingual.net/

There are instructions about how to install the script in Firefox (with Greasemonkey) or Internet Explorer. You then need to add translations to their wiki. I have done a basic translation of some terms for Spanish.

To reduce loading times you can copy your translations and the script into your own local Greasemonkey script, so there is no delay looking up http://mylingual.net/ every time you visit the page. It works just great (although you can’t change button images)