Howelsen Hill in Steamboat Springs (always low cost)
Howelsen Hill Ski Area is a historic ski area and Olympic training grounds operated by the city of Steamboat Springs, and is one of the only ski areas left in Colorado that is affordable on a daily basis. This ski area is a decent place for downhill skiers and snowboarders to make some quick laps, and features a nice terrain park, but it is especially nice for Cross Country / Nordic skiers.
There are only a handful of downhill runs served by 1 rope tow and 1 chair lift, but there are miles of Nordic trails. Howelson is lit for night skiing and often stays open until 8pm.
Oh yeah, the huge ski jumps are off limits to the public but they are an amazing sight!
2012 - 2013 Rates:
Lift Tickets: $20 per adult, discounts for children and seniors.
Terrain Park Only: $10
Nordic Trails Only: $10
Children's Magic carpet learning area: Free! (see concession booth for a free ticket).
$10 night skiing tickets are also available Tuesday through Friday.
Full lift ticket pricing breakdown for 2012-2013: 
Hours and Season:
CLOSED MONDAYS.
Tuesday 1:00 pm – 6:00 pm
Wednesday 1:00 pm - 8:00pm
Thursday 3:45 pm - 8:00pm
Friday 10:00 am - 6:00 pm
Saturday and Sunday 10:00 am – 4:00 pm
Closed on Christmas Day and special holiday hours are in effect through Jan 3.
Howelson Hill Home Page and Maps: 
Steamboat is fairly remote for a day trip, but if you can't afford the lodging in the area, there is a year-round campground that is reasonable called Steamboat Campground.
Free Trips Random Panorama

Upcoming Colorado Free Days
-
Sat 05-25-13 - Mon 05-27-13:
Boulder Creek Festival -
Wed 05-29-13:
Golden Kayak Event -
Sat 06-01-13:
Super Cruise -
Sat 06-01-13:
Denver Art Museum