If you don't have either, then there is still a way to do this, but it's more of a "some assembly required" approach, and you may need a spare ATMega chip on hand*. You will need a solder-less breadboard for this, though.
There are full instructions here: http://arduino.cc/en/Tutorial/ArduinoISP
Look at the bottom under the heading "Circuit (targeting an AVR on a breadboard)"**
*I'm not 100% sure a spare ATMega is needed, and you can use the Ardunio as an ISP without one installed. I doubt it's the case.
**The method will work with the Uno board, and there are instructions for older boards too, if you have one.