As I plan my MR to pick up my paltry 1500 miles to maintain status, I put together a spreadsheet to track the CPM and thought the results might be of some use to others. I have put in only those with CPM<$0.10 and only domestic.

NOTE: the CPM is calculated on the base fare.
NOTE: Unless I end with DEN the fare is return via same itinerary

Flight dates: Depart 12/10, Return 12/12
DEN-TPA - $288 - 3012miles - $0.0956CPM - UA/CO
DEN-LAX - $162 - 1724miles - $0.0940CPM - CO
DEN-PDX - $190 - 1984 - $0.0958 - UA/CO
DEN-OAK - $184 - 1934 - $0.0951 - CO
DEN-IAH-MSY - $168 - 2722 - $0.0617 - UA/CO
DEN-IAH - $138 - 1722 - $0.0801 - CO
DEN-MCO - $299 - 3090 - $0.0968 - UA
DEN-PHX-GEG - $206 - 3242 - $0.0635 - US
DEN-SEA-PHX-DEN - $208 - 2735 - $0.0761 - US

Flight dates: Depart 12/11, Return 12/12
DEN-TPA - $228 - 3012 - $0.0757 - UA
DEN-LAX - $118 - 1724 - $0.0684 - UA
DEN-PDX - $158 - 1984 - $0.0796 - UA
DEN-MSY-ORD-DEN - $168 - 2790 - $0.0602 - UA
DEN-IAH-AUS-DEN - $197 - 2130 - $0.0925 - UA
DEN-MCO - $288 - 3090 - $0.0932 - UA
DEN-PHX-GEG - $201 - 3242 - $0.0620 - US
DEN-PHX-SEA - $208 - 3422 - $0.0608 - US

Flight dates : Depart/Return 12/11
DEN-TPA-ORD-DEN - $228 - 3406 - $0.0669 - UA
DEN-LAX - $118 - 1724 - $0.0684 - UA
DEN-PDX-LAX-DEN - $252 - 2688 - $0.0938 - UA
DEN-SBA-SFO-DEN - $178 - 2383 - $0.0747 - UA
DEN-MSY - $168 - 2130 - $0.0789 - UA
DEN-IAH-MSY-DEN - $188 - 2426 - $0.0775 - UA
DEN-SAT-IAH-DEN - $138 - 2155 - $0.0640 - UA
DEN-PHX-SEA - $208 - 3422 - $0.0608 - US

Not really sure where I'm going just yet, but at least I have options. DEN only seems to get super fares when WN or F9 are putting the screws to UA.