Whether you are planning a large layout for a show or a small bedroom setup, you'll more than likely want to diagram it all before you begin.
Download BlueBrick created by Alban Nanty
This software was designed specially for the AFOLs who want to prepare the layouts of their LEGO® exhibitions. BlueBrick is compatible with LDRAW and "Train Depot Track Designer" and was designed to extend easily its part database. Its layers feature allow you to better organize your map, and some specific layers make possible the addition of annotation and area assignment. RAILBRICKS Recommends!
Monorail Network Planner
http://monorail.sariel.pl/ created by Paul Kmiec
This online tool lets you design a layout of a Monorail network, using all types of the Monorail track sections.
LEGO Model Scaler
http://scaler.sariel.pl/ created by Paul Kmiec
LEGO Model Scaler allows a user to upload an image, then add dimensions to the image based on LEGO brick and stud scales. Useful for creating realistic models from prototype source materials.