For a while now, I've been looking for a simple wiki to manage my personal notes and to do some basic shared editing. After looking through the vast number of wikis on WikiMatrix and still not finding what I was looking for, I ended up doing what hundreds have done before me: wrote my own wiki, and threw it on the pile of exitsing ones.
Up until recently, I've been using TipiWiki as my notebook, which is very light, simple, and easy to deploy. However, recently started running into its limitations, including limited markup possibilities (e.g. no multi-level lists), the lack of decent history (seeing who changed what, when), … I liked the idea of git-wiki, which used Git as its backend, giving it good history support, and the fact that all documents are in a real repository. However, git-wiki uses Sinatra, which requires way too much valuable resources than I want to spend on a simple wiki.
So, I took the idea of using Git as a backend, threw in the Textile PHP class for marking up text, and wrote WiGit: a simple, themable wiki in PHP (which is less cool, but also less heavy than Ruby/Sinatra), built upon Git, with history support, basic user support (from HTTP authentication), and pretty URLs. The default theme is still rough, and there are still a bunch of features coming up, but it should function properly already as a simple wiki for your everyday needs.