I also recommend TRAC. And I recommend my ISP too - WebFaction - which gives you integrated SVN/TRAC out of the box, along with any database or programming language you need. A small slice costs $9.50/month.
We use DevGuard for SVN/Trac hosting. They start at $6.95/month. I'm surprised Trac is the YC top-rated tool for project management tho; they don't have anything I would call a "project management". It's a basic bug tracking system.
FYI, Trac floated to the top when i asked this same question a few months ago:
FYI, Trac floated to the top when i asked this same question a few months ago:
http://news.ycombinator.com/item?id=124253