There might be an above-ground lava source nearby (which is a VERY rare and neat occurrence). If there is, mark the location somehow and build a house around it.
I wandered for quite a while and found nothing, but when I returned after locating something else I found a lava flow coming out the side of a mountain. I also saw strange light sources on the ground, coming from nothing but still glowing.
I can't put out the forest fire, I've coated trees in water and come back to find floating fountains with a stump at the bottom. I'm a little worried it will reach my housing area, which is still very far away.
I did finally manage to find a snowy region on this map (I dumped my first map when I swapped computers, and found this map to be even more entertaining than the other.) I've been looking for one ever since I found out he was going to put snow in the game.
I built a mine all the way to the bottom of the map, like I always do, and I spent a good amount of time carving out a massive area around any lava pits, but the coolest thing I found was when I happened into a cavern that led all the way to the surface, directly outside my large mountain castle.