I put mine in the photo album.
I noticed some posts told you to pitch them. I wouldn't. There are a lot of other things you can pitch out to declutter yourself that are less meaningful. I save even the ones we don't get to see very often, even the ones I haven't seen in person yet. This way I can see how they grow and I'm thankful. fb isn't the same. If I knew someone was pitching out the photo card I sent, I wouldn't bother sending one again. It's a thoughtless thing to do.
I save all my Christmas cards and a lot of others too. And no I don't have clutter everywhere. I just have a couple boxes under the bed. Now and then I go through cards and letters and throw some out, but most I keep. These things mean something to me and may to someone else when I'm gone. When my mother died suddenly, I was thankful for her letters and my father gave me back the ones I wrote to her.