By a car
This method is for long in use in Australia, including during championship where more than hundred hanggliders were launched by this way, each team was assigned a corridor parallel to the others. The several hundreds meter long line is hooked to the car via a dynamometer which the driver is monitoring during the climb so as he can regulate the tension (the speed).
A more sophisticated method using a cable unreeler regulated in tension has been successfully developed, it requires less space on the ground as at the start of the takeoff roll the glider is short behind the car. Watch the movie.
There are little winch especially developed for hangliders and paragliders, which are perfect for ultralight gliders launch. They are usually regulated in tension, which provides an excellent safety level. The lines are in kevlar.
A winch for gliders is normally inappropriate for ultralight gliders: too much power, too high winch speed, steel cable too heavy, it would generate too strong a load on the structure of an ultralight glider.