I bought a copy of Photomatix recently - been wanting it for ages but just figured they do a massive 60% student discount!!!
The software allows me to render tone mapped HDR images straight from Lightroom - awesome!
An HDR is a combination of several images, over and under exposed in order to get more levels of detail in the shot. Here's a sample of the effect (slightly exaggerated here) - a view from my home office window.