Denver is a major metropolitan city and as such as a broad selection of museums, galleries, shopping, and site seeing. What do you like to do and do you want to stay in the city or migrate out some distance?
The lower downtown area, Lo Do, is home to lots of trendy restraunts and brew pubs as well as Coors Field, home of the Rockies baseball club.
Larimer Square has artsy stuff and eateries in Victorian era buildings and is hosting Snow Fest while your here. If the weather doesn't cool down, I don't know how well that will go over.
16th St Mall is a mile long outdoor shopping opportunity in downtown.
Pepsi Center is home to Nuggets basketball and Avalanche hockey, but no games are scheduled during your visit.
The Denver Zoo is pretty impressive and being in a central city park, is an easy walk.
As a pioneer boom town, Western stuff abounds like the Colorado History Center, Museum of Western Art, Buffalo Bill grave, and Four Mile Park.
You leaving few days too early to hit the Tri-State swap meet, biggest car parts swap in the area, which runs Feb 7-8.
Cuda Hunter, 1 Wild R/T, and dfrazz have some good suggestions too.