J.P.
There are a lot of good ideas, but I thought I'd throw one more into the pot: out daughter is 2, & until she is old enough to truly express herself what a wonderful dad she thinks she has, my way of telling him how much I appreciate him has been, & will be, to give him the day off. We'll take him out to breakfast, but I'll be fully responsible for the little one & her needs. And after that, he's going to go & do whatever he wants. That's what he's given me for Mother's Day, & it's been glorious! ;-)
Happy Father's day to all the wonderful men out there!