which is the best Blu-ray disc to show off my brand new projector?  

Check the sticky Quality Tier thread up top. Anything Tier 0 or Tier 1 would be good. My personal recommendations would be:

Black Hawk Down
Tears of The Sun
Kingdom of Heaven
The Descent

Kathy, the search engine would bring up threads and previous discussions. Use advance search, title search only, limit search words to one or two. And highlight this forum from the list to the right. Words like reference, best and top will bring up all the past threads. As Firefighter pointed out there is a sticky at the top of this forum that covers what you are asking for.

Ron

There's a sticky at the top of the forum.