Redmine is pretty nice and for small projects you can host it for free on an AWS micro instance (pretty easy to setup with something like bitnami). For open source projects JIRA is also free.
I'm not familiar with anything .NET based that has similar functionality. Redmine was pretty easy to setup and configure. If you just want issues/roadmap/repo, that's probably what I would go with. If you're just looking for a fancy todo list you could try something like trello or workflowy (not open source, but free).
