What Task and Time Management tools are available?

How about Gnome Planner? http://live.gnome.org/Planner

Another one is TaskJuggler: http://www.taskjuggler.org

If you already use KOffice then KPlato is there for you: http://www.kde.org/applications/office/kplato/

Last but not least, for only task management there is http://ginatrapani.github.com/todo.txt-cli/ One of my favorite, a command line utility, really awesome!

Maybe Tine 2.0 is an option, it has a very good calendar and task module. Horde Groupware can be good as well. If you need project management, PHProjekt may be worth a look.