Google code provides a great integrated experience with Subversion repository. You can login into Google code with your GMail username. But be careful, you should use "GoogleCode.com Password" instead of the GMail password. Or you won't be able to authenticate and will get the following error:
svn: PROPFIND request failed on '/svn'
svn: PROPFIND of '/svn': authorization failed (https://projectname.googlecode.com)