I'd recommend Trac (trac.edgewall.org). It's pretty configurable with basic milestone tracking and a wiki (and people have written addons, etc.). It also integrates with Subversion.
http://www.redmine.org/wiki/redmine/Features
While you're at it, consider a continuous integration tool. Hudson worked great for us:
FYI, Trac floated to the top when i asked this same question a few months ago:
I want it to (a) track bug issues, (b) track milestones and a roadmap, (c) allow us to upload code to keep track of each of our changes to the code, and (d) give us a (login-restricted) wiki and/or forum so we can document the discussions/ideas we have.
I'll take a look at Trac in more detail later tonight, but if anybody knows off the top of your head if Trac (or some other software) does the things I mentioned above, let me know!
The wiki not only works for arbitrary documents, but it's pretty well integrated elsewhere. For example, a ticket submitted to Trac can use wiki syntax. The tickets can also refer to Subversion revision numbers.
As an Apache server it can be authenticated in the usual ways.
Check http://www.redmine.org . It's the same as Trac, only with multiple projects and multiple teams/roles per project.