If you are going to Denver, have you booked your flight yet?  Thanks to Nick M, I learned about cheap flights on Southwest.com.  They have flights on Wed out and Sat return for $79 / one-way.  On Sunday, they return would be $89 / one-way.  That's still cheap to get a weekend in Denver!

 If you'd prefer something other than Southwest, another cheap flight is Frontier Airlines out of Midway airport.  They have RT tickets for a litle over $179.  You can't go wrong with this one either AND it seems like it isn't a sale price since Frontier has a hub in Denver.

The flight costs on these two airlines are virtually identical for a Wed-Sat trip for the Expo.  If you like the big guys (American or United), they may be offering fares close to these fares on their own websites.  Use their sites and you can usually save at least $5 on th cost of the fare, which is added by sites like Expedia or Travelocity.  That's why they all say they have the lowest fares on their own sites.

See you in Denver!