The unofficial guide to the AA program is located at http://home.webflyer.com/fewmiles/AA/
The guide to the UA program is located at http://members.aolcom/millionmileflyer/main.html
These sites give a practical guide as to what you can expect at various elite levels within the airlines' frequent flyer programs. Note, however, that if a certain benefit really appeals to you or there is some confusion, be sure to call and verify with the airline as these benefits are, as always, subject to changes.

I wish DL had something similar.