Soon you can get your hands on the Mobot modular robot for a very reasonable $270 a module (pre-orders available now). A number of connection plates and attachments will also be available, and I guess you can 3D print your own stuff.
I like the gripper that is powered and controlled by the rotating faceplate. I am sure the same concept can be used to 3D print some cool things in the future. A connector would be an awesome thing and definitely worth a price of some sort.
In general, it seems to be a very competent modular robotics system. It uses a snap together connector, making it simple and fast to use, but maybe not as strong as a system that screws together.
There is a Graphical User Interface RobotController, and you can program it with the C/C++ interpreter Ch so everyone from beginner to hard core hacker should be able to do some really cool stuff.
More info on Barobo.com