Here, use this and just plug in your neighboring airports

http://www.farecompare.com/search/compareDestinations.html?departure=DEN

i.e. airports such as SLC, that is nearby with low coast flights or within driving distance, but also is big enough that have international flights. i.e. airports at Boulder would not qualify. :)

PHX and TUC, FLL/MIA/PIB, or LAX/BUR/SAN would all be perfect neighboring airports.