The PRT-11417 Arduino Stackable Header Kit - R3 by Sparkfun is made to work with the Arduino Uno R3, Leonardo and new Arduino boards going forward.
They are the perfect height for clearing the USB-B connector and great for stacking multiple shields. This kit includes 4 headers (2x 8-pin, 1x 10-pin and 1x 6-pin), enough to connect a shield to an Arduino board. These are the same headers we use in our tutorials and with our own shields.