Trac.( http://trac.edgewall.org/ ) Its not wonderful, but from what I've seen, for SVN its the best.
With Access control to boot.
I managed to set up a rig with even per-directory permissions for various trac users ( they just didn't appear ) .
Been a while tho.
Default Skin looks pretty good, and is highly tunable.
Comes with a wiki & bug tracker, which you can disable if you want.