The Raspberry Pi is quite in the middle between the $200 all-you-can-eat boards (like the PandaBoard) and the Arduino clones for $10.
There is one board that I would buy if I did not have a Raspberry Pi: The BeagleBone Black for about $45.
If you compare them:
BeagleBone elec. connections:
- 3 I2C buses
- CAN bus
- SPI bus
- 4 timers
- 5 serial ports
- 65 GPIO pins
- 8 PWM outputs
- 7 analog inputs
RaspberryPi elec. connections:
- 8 GPIO pins
- 1 UART interface
- 1 SPI bus
- 1 I2C bus
And the BeagleBone board is open source - so you can use it for any projects you want.
Another nice looking board is the
Cosmic Board:
If I would have more free time I would buy the
Parallella board.
This is about a ARM A9 processor which has got access to a Epiphany chip which consists of a scalable array of
16 RISC processors programmable in C/C++ connected together using a shared memory architecture.
So this little board has a FPGA and an array of 16x700Mhz =
11.2 Ghz processor grid.
If you are able to get your c++ code using all the cores.
But a perfect and cheap start into massive parallel computing.