I was amazed to learn that aluminum can be cut by a hobbist with "normal" power tools.  A masonry cut-off wheel was used.  I put one in my 10-inch radial-arm saw.  DO NOT use a metal cut-off wheel.  They will clog-up with melted aluminum and will not work.

I purchased masonary wheels at Home Depot that did not work.  The brand above (Vermont American) was purchased at Sears - works great.  Be careful - wear a face shield and safety glasses.  Read the directions.  They can explode!

The cutting is done in the reverse direction of normal wood cross-cutting.  Pull the arm out over the top on the aluminum and cut by pushing the back of the blade into the work.  Only remove a very small amount each pass.  Lower the blade after each pass. 

Read you own safety manual for your saw and blade.  Do not do anything that goes against those directions.  Before attempting this procedure, consult with a metal cutting expert.  There may be safer more affective ways to cut aluminum.