This is a very simple cobblestone generator that I use on my server. It is compact and clean with a small redstone clock attached and has a 100% return rate. :D If you have any questions just ask.

Thanks, BgDemonic

Update #1

Check out my new YouTube channel

www.youtube.com/user/BgDemonic?feature=guide

Additional Notes

The texture pack I use is a combination of several popular texture packs such as JohnSmith and Gerudoku.