#tinkerbot

1. Moss

"With MOSS there is no need wiring your construction. The power and data are sent through an elegant single button contact, while the ground passes through the steel spheres."

Educational Guide Quality: Excellent 

Price: Very Expensive

Playtime score*: 4/5  

Expandability Potential: Good

Current # of modules**: 18

Programmable: Yes

Arduino compatible: No**

How it works: http://www.modrobotics.com/moss/moss-getting-started/

Learn more: http://www.modrobotics.com/

2. Little Bits

"littleBits is the easiest way to learn with electronics. It's an ever-growing library of electronic modules that snap together with magnets so you can invent anything!"

Educational Guide Quality: Excellent 

Price:  Very Expensive

Playtime score*: 4/5  

Expandability Potential: High

Current # of modules**: 60+

Programmable: Yes

Arduino compatible: Yes

How it works: http://littlebits.cc/intro

Learn more: https://littlebits.cc 

3. Tinkerbots

"TinkerBots is a toy building set with easy-to-add robotics that make it possible for young children (and adults, too) to create an endless number of toy robots simply by snapping together TinkerBots’ patented “Power Brain,” kinetic modules and passive pieces, and even LEGO bricks. No wiring or programming required. TinkerBots is like “living LEGOs."

Educational Guide Quality: Very Low** 

Price:  Very Expensive

Playtime score*: 3/5  

Expandability Potential: Good

Current # of modules**: 19+

Programmable: Yes

Arduino compatible: Yes

How it works: https://www.youtube.com/watch?v=EeLEUVqQk_w 

Learn more: https://tinkerbots.net

*based on estimated # of enjoyable hours with the system

**as of dec 2014