TaskFreak! , a simple but efficient web based task manager / todo list written in PHP
Some of it’s advantages & features:
It’s easy setup with MySQL or SQLite (PHP4 and PHP5 compatible)
It’s simple and easy to use (wickedly user friendly)
You can order tasks by priority and deadline or organise by project and context
It’s absolutely free (although you can sling them a few bucks via PayPal) & open source (Yaaay)
You can find a demo here and Ajax is on the way.
Oh yeah, it’s “GTD compliant,” though I’m not entirely sure that means much to most people out there.