When I first got my Pi I couldn't wait to take my programming from the web and into the real world, activating LEDs, servos, sensors etc. and although the Raspberry Pi is sold as a $25 piece of kit that can easily be replaced if you break it. The fact is right now they are like gold dust and you're probably better of breaking your arm, much easier to replace!
So I purchased an Arduino nano http://arduino.cc/en/Main/ArduinoBoardNano
It has 14 IO pins and plugs directly into a breadboard making it easy to hook up to other components.
You can hook up the nano to your Pi with a simple USB cable. You can also plug the nano into your PC directly. The output pins are well documented and the Arduino site has lots of documentation, coding examples and IDE software that will run on most OS's.
Once I get more comfortable with electronics I will interface directly with the GPIO pins on the Pi and hopefully by then the Pi will be easier to source/replace.
I'm expecting a delivery today of:
2 medium servos and a pan+tilt bracket so that I can mount my camera (or a laser which is also arriving or IR thermometer to create a basic thermal camera).
1 small servo so that I can try make a remote shutter release for my camera
Some LED's and a 74HC595 Serial to Parallel Shift register so that I can create an LED matrix.
A light sensitive diode to turn things on and off when it gets dark
Can't believe it's taken me this long to get into hardware.