Tus found the Ogre belt from an Ogre. It reduces your encumberance (more commonly known as your weight bar) by 20%. There is no speed penalty, etc.

As far as I know, Titan Belt and Troll Belt are not found yet, but we'll see what happens. ;)

[update]: Heart emailed me to give some more information on the belt. She loaded herself up to 100% and then used the belt. It lowered her to 68%! That's a significant reduction! Based on her CON/STR, her max carrying capacity is 2100. With the belt, if 68% is 2100 that means 100% is around 3100. In other words, the ogre belt is actually expanding her capacity +50%

We don't know if the weight increase is constant (+1000 units) or relative (+50% of your max), more info will be posted here as it is discovered.