Here's a really cool Valentine's Maze courtesy of Family Fun. They have a whole passel of printable stuff to keep your little Valentine busy.
Here is a heart-shaped Backyardigan's maze from Nick Jr. and the rest of their Valentine's printables.
Blackdog has some increasingly difficult heart-shaped mazes for the child who likes a challenge. Or, make your own maze.
Here is another and another and another. Can you tell my kid really likes mazes? And more.
This one is interesting - you have to count your way through the puzzle. This one is simplest, buy they have others counting by 2s through 5s.
The thing is, my 5 year old broke and dislocated his arm today at the elbow, so instead of him running about like normal, I'll need to keep him calm and busy and he will stay put for these. I got them each a book of mazes before Christmas and he had done the entire book within 24 hours, but my goodness it kept him quiet!