These are the bigger ones here in Colorado I have on a regular basis. There's a TON more smaller ones, but I don't have beers from them quite as often.
Odell Brewery -
http://odellbrewing.com
New Belgium -
http://www.newbelgium.com
Breckenridge Brewery -
http://www.breckbrew.com
Left Hand Brewery -
http://www.lefthandbrewing.com
Great Divide Brewery -
http://www.greatdivide.com
Avery Brewery -
http://www.averybrewing.com
Wynkoop Brewery -
http://www.wynkoop.com