I lived in Denver for 4 years. If you want a fun night out go down to LODO(Lower down town) the warehouse area that Coors feild is in. Lots of great bars and restaurants. Boulder is a nice trip, really only about a 30 min drive. hang out in LODO before the hockey game, if you want to walk a bit I used to walk to the games but you are looking at a 20 minute walk. There is a bus that goes through the middle of down town the 16th street pedestrian mall that is free. Give it a ride to check things out.
The Denver Art Museum id pretty cool if you like that sort of stuff.
I lived there ten years ago so things are a little foggy. Can't remeber the name of alot of the bars I went to or if they are even there anymore or not.
There are also some good bars and food in Washington park by the governors mansion. Most of the other things I would have suggested are only summer type things.
Skiing id=s great of course in Vail, but that is about a 2 hour drive. A little closer would be A-Basin, Keystone, or Brecken Ridge.
There is also the Coors Brewery Tour in golden, just a 20 minute drive.There is good food, shopping and bars in Larimer Square as well.
Just trying to remeber everything. There is a six flags in Denver but pretty sure it is closed in the winter.
Check out his web site:
http://www.lodo.org/
I spent most of my weekend evenings in LODO, just a great place to hang out at night.