The mbed Microcontroller is made for prototyping, and comes in a 40-pin 0.1" pitch DIP form-factor so it's ideal for experimenting on breadboard, stripboard and PCBs. It is a uC ScratchPad for trying out new ideas.
|From Hyper Embedded - Microcontroller ASIC and EDA|
The mbed Compiler lets you write programs in C++, and then compile and download them to run on the mbed Microcontroller. The mbed Compiler is a Web-App in the Cloud, you don't have to install or setup anything to ignite your first mbed project idea. Any OS, Any Where, your software is online and ready to use. You will need a computer or netbook with a Browser.
Two XBees and One USB Explorer
"I had two XBee modules that I really wanted to use with the mbed. These are the standard OEM RF Modules one with an antenna and one with a ANT chip. For one of the chips I will be using the Xbee Explorer USB from Sparkfun...."