My Jewish friend started sending me Rosh Hashana cards when I converted, and when I got it this year with two babies on it, i realized I'd grown up enough that I probably should make some, so I did. :) I only sent out like seven because I got a pack of ten and had to be stingy because the synagogue gets all huffy if someone doesn't get equal treatment.
I'll probably send the rest of my friends Thanksgiving cards. My best friend's family (who are Christian) do this, and I like it.