OpenTTD is the open version of Transport Tycoon Deluxe, you can download it from:
http://www.openttd.org/en/download-stable
In this game you are a transport company and your business is build commercial paths (roads, etc) and manage the transport of goods/materials in the map with different vehicles (trucks, vans, boats, etc...).
The learning curve is a bit hard if your are a "Angry Birds" player :-P
Download the zip, extract, run the exe, in the main screen go to "online content" and download these packets:
- OpenSFX
- OpenMSX
- OpenGFX (this packet is downloaded at the first boot)
for sounds, musics and graphics.
Also... do you remember Roller Coaster Tycoon?