You can checkout the latest source from the SVN repository trunk.
svn checkout svn://rubyforge.org/var/svn/redmine/trunk
This is the prefered way to get Redmine if you want to benefit from the latest improvements. By using the SVN repository you can also upgrade more easily.
Latest release: 0.5.1 (2007-07-15)¶
Redmine releases can be found at RubyForge.