Free SDK: Project 2010 SDK
MS Project is an important management tool that has only a small number of developers, so the opportunities are pretty good. You will need to own MS Project, and if you are a student or professor you get MS Project for free through MSDNAA. Once you do this you can download the useful Project 2010 SDK from:
Professors
Use this SDK in software development classes to teach how to use Software vendors SDKs, and important skill and is a potential interview question for your students
College Students
Mangers use MS Project and knowledge about how to program MS Project is impressive. Pretty easy to learn how to use MS Project