Have you tried picking some up and throwing them into the little tunnels in the side of the cliff?
With some experimentation, you'll discover that you can make a boulder fall through the bottom left and bottom right holes in the cliff, but not the one in the middle. (Note that in all of this my right/left are screen right/left.)
Find Video Games at Half.com
Free $5 on your first purchase and Get up to 50-90% off everyday! Buy and Sell previously owned Books, CDs, DVDs, Movies and Video Games.
http://www.half.com/ (Listing fee: $0.15)
Interactive Fiction - Best Prices at Bizrate!
Stop searching and start shopping! Click here and you’ll find great deals on Interactive Fiction at the best online stores, as rated by millions of customers like you!
http://www.bizrate.com/ (Listing fee: $0.04)
T-Shirt King has the Best T-Shirts in the World!
T-Shirt King has Birthday T-Shirts plus 1,000's of other licensed designs. Music T- Shirts, Funny T-Shirts, Movie T-Shirts, and much more. 100% Guaranteed. Free Email Newsletter.
http://www.tshirtking.com/ (Listing fee: $0.02)
NexTag Marketplace: Compare Prices and Buy!
Compare total prices (including tax and shipping) from thousands of sellers. At NexTag, find a great deal on computers, software, electronics, books, music and movies or sell your pre-owned stuff.
http://www.nextag.com/ (Listing fee: $0.01)
RPG Story - Interactive Fiction
Come be a part of our interactive choose your own path user created fiction! Many stories based in popular role-playing game settings.
http://www.rpgstory.com/ (Listing fee: $0.01)