MakerBot and RepRap have a lot of overlap in ideas and people. MakerBot founder Zach Smith is a long-time RepRap contributor and also runs the RepRap Research Foundation (http://www.rrrf.org/). MakerBot's "Cupcake CNC" fabricator is based on RepRap hardware and software. MakerBot also sells RepRap parts in their store.

The two projects are both contributing to each other, for example just today: http://blog.reprap.org/2009/08/one-of-my-partners-at-makerbo...