I'm an X-Wing player, and there are a couple Facebook Swap and Sell groups that see lots of activity with whole collections showing up at least once a week.

I'm considering trying out the LotR card game, and was wondering if there are any Facebook groups where people regularly sell off their collections?

I'd like to pick up a used core set with a saga or two if possible.

Nothing?

I don't know of any, sorry.

I would wager that LotR is the kind of game people don't sell second-hand. Since it's a solo game players are are more apt to just hold onto the cards for years (decades?) even if they are not actively playing. There is no meta or local player base to keep up with. Once in a while I'll see someone on the forums or Ebay selling a collection, but it is very rare.

Also, there is a sales section on cardgamedb that you may want to take a look at.

Boardgamegeek also has some sales sections.