If the weather is going to be around 50 degrees, go for a hike in the Flatirons. The Mallory Cave trail will get your heart pumping and it's stunning scenery. Royal Arch, 3rd Flatiron, Fern Canyon are other great hikes in the area.
Visit Eldorado Canyon State Park. Lot's of great hikes there, and it's one of the top 3 climbing mecca's in the United States. Just look up at the sunny walls and you are bound to see someone climbing up there.
Make the quick drive to Golden and take a free tour at the Coors Factory. Or if you just want to skip the tour and get to the free beer, ask for a pass for the "short tour" and go straight to the bar. I believe it's still three free beers. Blue Moon is on top there in addition to the standard Coors fair.
Go ice climbing in Rocky Mountain National Park.
Get a Colfax Hooker in Denver.
Go sled neckin' with Milo and kick him in the nutz...