Fuu... I am sorry, but I won't have time to do the video this week. Instead, I'll post some screenshots, links and descriptions.
The render program we use is Blender with the Cycles rendering engine. (
http://blender.org)
Some very good blender introductions and tutorials are available here:
http://blendercookie.comUse the jMC2Obj (
http://code.google.com/p/j-mc-2-obj/) converter to export buildings and regions from your Minecraft worlds.
Simply select your world folder and click
Load.

The second step is to select the region you want to export. After you have selected this region click
Export Selection. Choose a path where you want the exporter to write the OBJ files and make sure
Do not allow duplicate vertexes in the
Show more options... options is checked.
You will also need to export your textures. Click
Export Textures, set the pre-scale factor to 16 and un-check
Export alpha channel in separate files. If you want to use a custom texturepack click
Custom texturepack and select the ZIP file.

In Blender:
Import the OBJ file you have exported and change the renderer to Cycles. You need to setup all the materials now. Select one of the imported objects and click
Use Nodes in the materials panel. You can setup your materials if you switch to the node editor now. I have two examples (1 non-transparent and 1 transparent material) prepared:


The last step is to setup your scene, camera and light and you are done. I highly recommend that you use an environment texture for the "World Material". You can get great environment and sky textures from
http://cgskies.com
If the result of your render is not awesome enough you can always use the compositor to tweak the result a little bit. I've also prepared an example for a vignette effect:

Ok, again: sorry that I wasn't able to produce a video. If you have questions ask me or Mike. - I hope that helped a bit.