First, there is the Santa Cruz Skateboards group.
This particular group is, as the name suggests, dedicated to the skateboards of one of the great company names in skateboarding. It includes everything from Santa Cruz decks, stickers and apparel to skaters who have skated with Santa Cruz.
The second Flickr set I wished to share is not a group, but rather the Flickr set of a particular user "sreptone" who has amassed quite a collection of decks, including some that you do not see particularly often.
Check them out -- but be prepared to spend a little time!