We're just a two-man shop in the middle of Central Illinois. I called to have our Oracal sales rep stop by the shop after we bought our printer and he had no problem coming through when he was in the area. He gave us samples of media and at least one copy of every guide they have including a color fan, which is way more convenient than the guide books. I think they actually like taking a break from the normal routine and stopping by shops from time to time, even a small shop like ours.
Aside from that, the obvious answer is trade shows. Every time we go to a trade show, we grab every color chart we can. I don't remember the last time we actually had to pay for a color guide.