I was looking for a way to re-use my stuff to program an ATTiny13, a uC from Atmel.
I founded this tutorial explaining how to use your Arduino UNO as a programmer: http://www.instructables.com/id/Updated-Guide-on-How-to-Program-an-Attiny13-or-13a/
I decided to build a shield in order to facilitate the operations.
This is a very simple project: I needed less than an hour to finish it.
I just followed all the instructions of the tutorial, but I soldered them on a prototype board.
In order to facilitate the understanding of how I made it, I designed it on Fritzing:
In order to facilitate all the operations, I put in a DIP-8 socket to plug my ATTiny.
When you try to plug your shield on your Arduino, make sure that all the pins are correctly aligned.
To use my Arduino as a programmer, I followed all the steps of the tutorial above.
It's very easy and useful.