I have a little coffee area in my house so I have the fanciest variety on display in my kitchen, but beyond that I haven't found a good use for them. Good to know they have a lot of value!
I used to just sell mine directly to Reese, but I'm going to start displaying them with the other Brewster items as part of my cafe room. I also might send a few to my favorite villagers, just for fun. For some reason, I never thought to do that until reading this post.
I sell most of them because they stack up surprisingly quickly and sell for a decent amount, but I use the rest as props in the cafe themed room in my house. However I'm pretty sure they lower your HHA score so oof.