I wanted to run a Wiki at work, to handle all sort of issues.
I already am using Media Wiki, but this requires MySQL database, and I didn't want to have to install that. I tried to install Trac, and I did manage to install it, but afterward it was... "Okay, now what?"
I then found out about ScrewTurn via Avery, and decided to give it a shot. It has an installer that I downloaded, and in 5 minutes, I had a fully functional Wiki. The only issue that I had was that the installer didn't setup the file premissions, but that took a second to fix. I got it running, and it is a lot like MediaWiki, except that I don't have to do anything to get it to work. I am very impressed.
Now all that remains to see if I can put it to good use :-)