Sailing is mostly on smaller lakes in the Denver area but it is certainly alive and well. The ice is usually off by about mid March and April, May, June are good sailing months. July, Aug and into Sept can be light winds and you can sail up to about Thanksgiving if your the hardy type.
Some links:
http://hobiefleet61.org/
http://www.cherrycreekmarina.com/
http://www.denversailing.org/
http://www.marina42.net/cgi-bin/p/m42p- ... -anchorage
Or at Dillon res up in the mountains:
http://www.dillonmarina.com/
We were ice boating at Dillon this last Saturday
http://iceflyer.com/picture/Dres12_06_4.jpg
http://iceflyer.com/picture/Dres12_06_1.jpg
http://iceflyer.com/picture/Dres12_06_2.jpg
http://iceflyer.com/picture/Dres12_06_3.jpg
I also sail at Elevemile which is about 100 miles from Denver to the SW
http://analogengineering.com/elevenmile/lake_shots/