I've recently been using Basecamp for some project management. It was working fairly well. I can definitely see the value if you are a consulting firm or similar where you are manageing multiple clients/projects. The main drawback relates to their claimed strength of simplicity. Sometimes it's too simple. I'd like to see multiple todo pages for one. Also, my real complaint is speed. Basecamp seems very slow to me, painfully slow at times.
On a new project, we evaluated Basecamp vs. using a wiki and sort of doing it ourselves. Due to various constraints our wiki choices were MediaWiki (which is what powers Wikipedia, and many more), or Confluence. MediaWiki definitely came up short. We have a range of people using this, from engineers to marketing folks. Wiki's sometimes present stumbling blocks to those who prefer to write in more of a word processor environment. Also, we really wanted a good task list system. We tried the two task extensions for MediaWiki, but neither seemed to actually work properly.
I then setup Confluence. It should be noted that it is not open source and has a significant price tag that may be a prohibitive factor for many (note to open source folks though that they have arrangements for that). Setup was simple drop-in and run a startup script (as well as create a database in your DB engine of choice).
I am impressed! Confluence is a superb wiki! I've used several other wikis over the last year or two (we use twiki heavily as well, and I've tried a half dozen others). Confluence takes it up a notch. It feels polished and professional, and it's been a joy to use. Also, the less-technical folks are finding it a lot nicer to use as well. And, their task extension (we're using the Enhanced Task List macro) is quite nice, perfect for what we're after (fitting our Scrum use).
Another thing I like is how it manages hierarchies of pages, and provides automatic lists of child pages at the bottom of a page. This allows you to forgo linking when you don't need to. Also, the mail features, and RSS abilities are well done. So, I'm sold, and we're proceeding full steam ahead with Confluence.