The Debian task selector.
I generally regard this as just part of debian-installer these days, but it is a separate project on alioth, with a slightly different set of committers, and a potentially broader set of uses than the installer.
Please read the FAQ.
Recent code changes
The most significant change since sarge is that tasksel will use heuristics to find machines that look to be likely candidates to run the desktop task (and the new laptop task), and will default to selecting the task on those machines. (Obviously it lets this default be overridden.) This is intended to avoid "my install ends in a black screen" bug reports from very novice users.
Tasksel had support added after sarge for selecting between the gome-desktop and kde-desktop subtasks via preseeding. It also allows derived distributions to pin the selection to one or the other, or even unhide both sub-tasks to allow manual selection between them.
I think that one obvious missing task is a task to perform backups of the system.
backupninja seems like the best thing to base this on. Since the task should include setting up backups as part of its installation process, quite a lot of work will need to be done to make this a reality.