I've just been converted to a tool called Redmine, a combination of the ubiquitous Trac and something like ActiveCollab. Able to work directly with Subversion code repositories, Redmine gives you support for multiple projects, per-project tasks, content management (blog, news, document management, wiki), both a calendar and GANTT chart to view progress, a very comprehensive user management system that can even authenticate against LDAP (i.e. Active Directory, NetWare, et al), and as always is an open-source application so you can improve/extend the code as you see fit. I'm trying it out at work but it looks like something I'm going to start using for all of my project management. Awesome stuff!