Looking for groups of DLC giveaways

I don't know of any and I doubt you will ever find any unless you start your own. DLCs are generally a hassle to give away, because too often, the Steam API doesn't allow for them to be properly detected as already owned. Giving away DLCs on a regular basis would be a major chore, with endless rerolls, and I don't see anyone with much interest in doing that specifically.

Unfortunately it's very unlikely for you to get into a gifting group without being an active gifter, and that's if there's any group dedicated to giving away DLCs at all. I second SickTeddyBear's advice and suggest starting your own group. You'll need to be willing to gift a few as well though, since I don't think you'll have many members if people think you're just there to leech on them. :P

There was a group, but I don't believe it was active for a good while when I left.