What GUI tools do you advise to improve the usability of Linux for those accustomed to doing system administration the windows-way?
Users new to Linux often get confused when they need to configure something: editing a text configuration file may seem hard to them, and they want a GUI to tick checkboxes and just get what they want. A short list includes: hardware issues, drivers, Xorg (especially!), performance, network settings, sharing, user accounts, etc.
P.S. I've looked through questions already asked here, and found that there's no real centralized list of applications. Let's unite our knowledge! Community Wiki ;)