Source of the Nile
Although the actual experience of going here is not that interesting, it may be worth it for the sole reason that you can go home and tell everyone that you visited the source of the longest river in the world. There is a small monument in the area dedicated to Ghandi. Some of his ashes were released here.
The Jinja market is in the very centre of town, and consists of multiple acres of colourful shacks squeezed on top of each other selling everything from chicken hearts to motor parts. Definitely a must see, even if you're in Jinja for one day. The easiest and best way to see the town is to flag down the nearest boda boda driver motorcycle which takes passengers and ask him for a tour. Pay no more than six thousand shillings however, for less than an hour tour.