PHP 5

Web-based, platform-independent

Multiple database support, currently MySQL and PGSQL

Easy installation

Easy to use

Multiple projects

'Watching' tasks, with notification of changes (email or Jabber)

Comprehensive task history

File attachments

CSS themes

Advanced search features (though easy to use)

Atom/RSS feeds

Two syntax options for task descriptions and more (Dokuwiki / plain text)

Voting for tasks

Dependency graphs

Activity Bars for projects and user activity

Comments

Roadmaps