I'd recommend github for source hosting. I've got multiple open source projects that I run or use that use github for scm and use lighthouseapp.com for ticketing. These are fairly large OSS projects with many many contributors and it works great. http://github.com/wycats/merb-core/tree/master and http://github.com/evanphx/rubinius/tree/master as well as a bunch of other smaller oss projects.

Both github and Lighthouse will give free accounts to open source projects.