NixCraft is an online community of new and seasoned Linux / Unix sysadmins who want to make the most of their OS. Find useful tips and commands that will help you manage your *nix environment.
Freshmeat.net Maintains the Web's largest index of Unix and cross-platform software, themes and related "eye-candy", and Palm OS software. The site has thousands of applications, most of which are released under an open source license. Links to new applications are added daily.