Let's be honest, you came here to see some glowing potion bottles, correct? The easiest and probably the most striking is the use of glow stick fluid. I will not attempt to produce my own glow stick fluid (and neither should you), it's not necessarily safe and the chemical components are expensive/difficult to contain/dangerous (depending on the fluorescent dye chosen). If you are interested in understanding how a glow stick works, NurdRage has an excellent tutorial on youtube: http://youtu.be/tItOOpyJP5k
The easiest (and cheapest) method of obtaining glow fluid is to simply purchase it at a dollar store. While most glow sticks sold in stores are non-toxic, try to purchase some that actually state it on the package. Start by activating the glow stick, then clip both ends off with a pair of shears or tin snips. Pour the fluid into the bottle, taking care to watch for glass (when you activate a glow stick, you are actually breaking a glass tube filled with peroxide).
Rather than fill the entire bottle with glow fluid - which would be cost prohibitive - I cut the solution with a 1:1 mixture of hydrogen peroxide and water. Generally, it takes two "bracelet" glow sticks or one "necklace" glow stick combined with the above mixture to noticeably glow. Depending on the color, temperature, and peroxide solution this mixture can glow for up to 48 hours. In all fairness, however, the intensity will drop by half over a period of every 2 hours.
I will add that, despite being non-toxic, do NOT drink this mixture.