This was a fun one! I spent some time with Jimmy Bogard on his tremendously successful open source project called AutoMapper. If you have not heard of it then you have no doubt, like me, wasted precious keystrokes on manually converting from one object type to another by mapping properties in code. AutoMapper helps eliminate the need for that completely and goes a step further by even making queries to a database more compact and concise.
He also spends some time talking about what makes for great open source projects - oddly enough its not what I thought he would say.