Here's some easy to follow instructions to get you set looking at your worlds in 3D!
Get this nifty little program:http://www.alpix.com/3d/TerrainViewer/
Install to a location of your choosing.
Export the following maps via Legends Mode [d]:
Elevation map respecting lake and ocean floors
Standard Biome + site map
If you wish for the viewer to show lake surfaces, export elevations respecting water level and then copy/paste the blue non-river areas (rivers come out blue as well, but make the map look bizarre). Use an image editor of your choosing, I offer no help in this regard.IMPORTANT!
Resize both images to 1024x1024 or smaller and save as DFRegionTexture.png and DFRegionHeight.png (.jpg may also work, untested). The default export's 2048 is too large for the Terrain Viewer and it will crash (bmps may also cause a crash).
Move the new pngs to the \maps and \colors folders of Terrain Viewer
Open up \TerrainViewer\maps.xml and add this inside the <maps> tag: <map name="Dwarf Fortress">
<terrain demfile="maps\DFRegionHeight.png" texturefile="colors\DFRegionTexture.png" altscale="0.4" />
<sky skyfile="skys\Sky_Gradian_Day1.jpg" />
The sky file is unimportant, you can change that in the viewer and you can change the one it loads by default if you wish.
The "altscale" variable determines how much z is given per degree of terrain variant, 0.4 looked the best to me, you may wish to experiment.
Run Terrain Viewer by clicking the .exe
Click Maps and choose Dwarf Fortress
Other fun things to do? Export a temperature/rainfall/volcanism/etc map and use it as a texture! See how they compare!