One of the most awesome pieces of software that I've come across in my career as a consultant and software engineer is Trac.  Among the various awesome features of Trac include:

• An awesome plug-in system and library for all sorts of add-ons to the core system
• RSS feeds on available on the timeline which acts as a customizable, almost realtime data feed
  
• Integrated source browser...it makes pointing out code isssues so much easier when you can link it to source
• An awesome wiki system that integrates with the ticket and changeset systems

Did I mention the ticket system?  Sure it lacks a bit in terms of workflow and it is rather simplistic -- being geared almost exclusively towards bugs, but I think the most important aspect that it brings is, well, tracking.

Having worked with it for almost a year, I find it really hard to imagine working on any sizable software project without it (or some other piece of comparable software project management tool).

Perhaps the only thing that I've found frustrating -- surprisingly, it is not with Trac itself -- is the inability to really win anyone else over in my group; you'd think its like pulling teeth to get a ticket created for tracking purposes instead of using email. Let's not even get into wiki editing or proper usage of wiki markup or taking advantage of the integrated wiki syntax for tickets and what not.  It just seems like some old habits are hard to break (much to my dismay).

But don't let this dissuade you! If you haven't given it a look yet, there's no time like the present to download it and give it a go. Oddly enough, if you're looking to get started, VisualSVN Server may be the way to go since it includes an integrated installation of Apache, Subversion, and a mangement console.  Also check out the awesome documentation on installing Trac on a variety of systems, including Windows.