This year's annual gathering is on 5-Sep-2015 from 3-8. If you are in Colorado and have never seen the Shelby American Collection I would encourage you to attend the party and support and visit the museum.
Ticket info (you can buy at the day of the party) and more detail are here:
Shelby American Collection Annual Party and Car Show | Shelby American Collection
This year the focus is on the 50th anniversary win by the Shelby American team of the 1965 FIA Manufacturer's Cup. There are always a lot of original Shelby American team members, great food and an open bar.
(Even if you aren't there for the party, and you're in the Denver/Boulder area, the museum is still worth visiting!)
(I also go the notice of the annual fundraising raffle, but I'll post it separately).