How can I start and stop services in Ubuntu with a GUI?
Well depending on how you define graphical, there is an excellent tool called SysV Runlevel Config.
First, install it:
sudo apt-get install sysv-rc-conf
Then start it with sudo:
Now you can go through a press the space bar to toggle services on or off at different run levels. This is helpful to disable the many things Ubuntu has on by default.