Dinosaur Ridge in Morrison (always free)
This park in Morrison, Colorado (southwest of Golden) is really an outdoor museum, where you can hike or ride a shuttle as you examine evidence of Dinosaur activity in Colorado. One of the popular Colorado attractions for kids.
Colorado Mineral and Fossil Spring Show
The free Colorado Mineral and Fossil Spring Show brings gem and fossil dealers from across the U.S. to the Denver area to showcase their huge selection of amazing finds.
Up to 85 Retail / Wholesale Gem, Mineral, Fossil, Jewelry Dealers From All Over The USA
When:
April 14-16, 2017
Location:
The Crowne Plaza Dia
15500 EAST 40TH AVENUE, DENVER, CO 80239
http://www.rockygems.com/colorado-mineral--fossil-spring-show-2017.html
Sunnyside Music Festival (mid-September)
The free Sunnyside Music Festival is a showcase of Colorado talent that takes place each year in Denver's Sunnyside neighborhood.
Denver Mountain Parks (always free)
The city of Denver operates a series of beautiful and diverse parks in the foothills areas west and south of Golden.
Snowmass Summer Concerts
On summer Thursdays and Fridays the laid back atmosphere of Snowmass Colorado comes alive with their free Snowmass Village Summer Concerts. The music, set up on a Snowmass ski run stage near the upper village, is loud and wild.
When:
Summer Thursdays (and sometimes Fridays) from 6:15 to 8:30pm.
Where:
Snowmass upper village.
Schedule:
The 2013 Snowmass Village Free Summer Concert schedule is as follows:
June 20: Freddy Jones
June 27: The Dunwells
Friday July 5: CJ Chenier
July 11: The Revivalists
July 18: Mountain Standard Time
July 25: J.Boog
August 1: Tab Benoit
August 8: Nigel Hall
August 15: Robert Walters
More Info from the Aspen Snowmass web site: 
Community Car Show and Drag Race
The annual Community Car Show in Littleton takes place Saturday September 12th, 2015, from 10am to 2pm. Admission is free both for spectators and exhibitors. The car show takes place at Heritage United Methodist Church and will include music, free snacks, and you will vote on the People's Choice winner.
After the car show, a drag race takes place from 4pm - 8pm at Bandimere Speedway in Morrison. Admission is free for spectators, and $30 for racers.
You are encouraged to bring a canned food item or good condition used winter coat or boots.
When:
Saturday September 12, 2015
Car show runs from 10am to 2pm.
Drag race runs from 4pm to 8pm.
Where:
Car show takes place at Heritage United Methodist Church:
7077 S. Simms Street
Littleton, CO 80127
(next to Chatfield Sr. High)
Drag Race takes place at Bandimere Speedway in Morrison:
Immediately off the C-470 Morrison exit.
Free Summer Bowling For Students at Brunswick Bowling Centers
Brunswick Bowling Centers are offering free bowling for students during the summer of 2012. Kids or their parents (depending on age) sign up for Brunswick's Bonus Zone to get free bowling.
There are a few Brunswick Bowling Centers along the front range that offer the free bowling for kids promotion.
Find a bowling center:
Bonus Zone Sign up:
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Keystone Ski Resort Free Scenic Chair Lift Rides
Keystone Ski Resort offers free summer scenic chair lift rides every Friday from 3-7pm, starting June 14 and continuing until summer activities close at the end of August. The views are incredible so I would definitely recommend taking a Friday to check out Keystone.
Golden History Center and Astor House (free days)
The Golden History Center, along Clear Creek next to the Golden Library, and the Astor House Museum, offer free days from time to time. The next free day is during the winter Candlelight Walk, December 5th, 2014.
Details from the Golden History Museums web site:
New Belgium Brewery Tours (Tuesday - Saturday)
The New Belgium Brewery in Fort Collins has had to greatly modify their previously awesome tour and beer sampling system. They never said why they changed, but it was obvious what the problem was when I visited. Because of the free beer samples, the place was overrun with college kids who wanted to party hard for free.
Now to get a small free sample you must take the full brewery tour, and reservations fill up online weeks or months in advance. If you go there without being signed up for a tour, you can still buy beer at the bar for a discounted rate.
Despite the changes, this is still an excellent small brewery to see and learn about.
Location: 500 Linden Street in old town Fort Collins.
Liquid Center Hours:
Tuesday - Sunday 10am to 6pm
Closed on Sundays until Feb 9th, 2014.
Guided Tour Hours:
Tuesday - Sunday 11am to 4:30pm
Closed on Sundays until Feb 9th, 2014.
New Belgium Beer Web Site:
Avery House, Fort Collins (free Saturday and Sunday)
The Poudre Landmarks Foundation has some of the best Fort Collins attractions for history buffs. Their historic Avery House in Fort Collins offers free tours on Saturdays and Sundays from 1pm to 4pm. The tour guides provide a wealth of information about the city's early days, and what life was like in the front range in the late 1800's. This is one of the great historical things to do in Colorado, as Fort Collins has a rich and colorful early history in the settling of Colorado.
When:
Year-round Saturday and Sunday
1pm to 4pm
For 2014, the Poudre Landmarks web site is incomplete and it is unknown whether Avery House tours are still taking place. Hopefully they will release an updated schedule soon. Call them to check on the latest situation: 970-221-0533
Where:
328 West Mountain Avenue
Fort Collins, CO 80524
Avery House Web Site:
U.S. Air Force Academy Visitor Center and Chapel, Colorado Springs (always free)
The United States Air Force Academy at Colorado Springs has a unique visitor center and chapel area that is free and open to the public. Visitors can learn a wealth of information about the academy and it's history as well as view the planes on display. The Chapel is absolutely beautiful and due to it's unique architecture it's probably the most photographed building in all of Colorado.
Denver Zoo Free Days
The Denver Zoo free days are by far the most popular Denver free days for families with kids, and are typically held during the fall and winter.
Euclid Hall Denver Happy Hour (Downtown Denver)
OK, I normally make it a policy to only check out Denver happy hours that have food specials with drink specials. However, when I saw that that 5280 had deemed Euclid Hall the best Denver happy hour, I had to check it out for myself. I went in skeptical, and came out satisfied and stuffed.