User-mode Linux.
The User-mode Linux kernel patch and uml_tools home page.
http://user-mode-linux.sourceforge.net/
User-mode Linux Community Site
Community site dedicated to User-mode Linux, contains links, docs, etc.
http://usermodelinux.org/
Bug Tracking System - Bugs
Tech Support Tracking System - Support Requests
Patch Tracking System - Patches
Feature Request Tracking System - Feature Requests