wojo, you didn't tell us what your skiing skills and preferences are, which could be a clue to what feedback we'd give. FYI last ski season I had fun at Eldora, Loveland and Winter Park and wrote about it for DCSki: http://www.dcski.com/articles/view_article.php?article_id=281&mode=headlines
Suggestions from others are good and all of the following may be doable:
Loveland ski area to Den airport: ~70 miles/1:30hrs
Winter Park ~90/2:05
If you just want one day of skiing I'd suggest driving up to one of the little towns along I-70 like Idaho Springs or Georgetown and spending the night there on the 16th in a mom and pop motel. Try a buffalo burger at http://www.buffalorestaurant.com/
. Then hit Loveland on the 17th. If you left Loveland at 3:15pm after skiing, in good weather, you should make it to airport by 4:45pm, plenty of time for 6:40pm flight (adjust accordingly for you own time management preferences). Loveland will give you a nice taste of high alpine Colorado skiing with small crowds and easy access to interstate hwy type roads all the way to airport. The only knock on Loveland is the sometimes high winds along the continental divide (wasn't windy for my visit though). BTW, Love's remarkable chairlift # 9 is currently open, here's the view from the top: http://bdagger.colorado.edu/~wachter/2002/04/Loveland/105-0587-98_PAN.jpg
If you really want to maximize skiing and do the night ski thing on the 16th then follow Roy's suggestion to visit Keystone. I think it's the only night skiing near Denver. Overnighting in Frisco/Dillon or anywhere back along I-70 towards Loveland should work to get to Loveland next day (or you could ski Keystone again the next day and head back to airport around 2:30pm.
Eldora is in a totally different direction west of Boulder in real pretty country. It's a fun ski area, but Eldora is below treeline and feels more like a gorgeous version of Snowshoe, than Colorado.
The Mary Jane/Winter Park suggestion is best for experts who want to ski big time bump runs. The drive back from WP to Denver goes over a major pass (Berthoud) that could be dicey if there are snow squalls.
Arapaho Basin is also best for advanced to extreme skiers, but is close to Keystone if you wanted that combo. I like Powderpigs line of thought about visiting a smaller (the term is relative) area if you've just got one day for an experience that is not so overwhelming or confusing.