I\'m working on a project:
Lots of good reasons why to do it in the other answers. Personally, I like knowing I can look back at code that "used to work before I tried to fix that bug"; a situation that occurs far more often than I'd like.
For my personal needs, I've found that fossil is a good choice. It is distributed, low ceremony, installs as a single executable file, and available for Windows, Mac, and Linux out of the box and portable beyond that. It provides a wiki and ticket tracking in addition to revision control. It has a built-in web server, used along with your browser to provide a GUI for management tasks, and useful for ad-hoc cloning and updates. It is easily integrated with a web host. Its home site is served by a copy of fossil, for instance.