Download SpringDownloader Here
Linux (Ubuntu) users, get mods in the rapid system this way:
1) Obtain the rapid tag of the mod. For example, for the test version of CA, it's ca:test.
2) Paste the following in the console, after replacing "<rapid tag>" with the rapid tag.
sudo aptitude install python-setuptools python-dev sudo easy_install rapid-spring rapid pin <rapid tag>
More information : http://github.com/tvo/rapid/