We just got back from camping on Cape Cod this weekend. We went down on Friday morning and camped at Shawme-Crowell State Park in Sandwich, MA.
It is a typical state park, nice wooded sites, no hookups, but hot showers (free!) and decent bathrooms.
This place is right on the cape. You just have to battle the traffic to get over the bridge and you are basically there!
It doesn't get the press of Nickerson out in Brewster (I think), but it was great and as a MA state resident it was $12 a night. $14 for out of state.
It took us 50 minutes to get out to the Cape Cod National Seashore visitor center and the beach at Marconi was great!
You can take the dogs on the beach on the national seashore as long as they are on a leash.
Regardless, the campground is a great alternative to the RV Resorts if you are looking for more rustic camping.
That's about it. Hope it helps someone.
Oh, one more thing, they are open year round! You can camp or rent a yurt. Thought that could be fun in February!
Jeremy