Purdue, 5 January 2012
This site has a tremendous amount of detail on a university senior project to develop a small launch vehicle. The stated goal was to "...find the most economical method to launch very small payloads (200 grams to 5 kilograms) into low-Earth orbit." This tremendous resource looks at various aspects of launch vehicle design in very detailed ways.
One can find the final reports as PDFs, the various programs used to perform the analyses and instructions on using the software.