I'm a big fan of his films, especially The Breakfast Club, Pretty in Pink, Ferris Bueiller, and Planes Trains and Automobiles.
She's Having A Baby is a particular favourite. It's not one of his better known films but it's worth checking out for all the cameos - Kevin Bacon hails a cab and the cabbie is Steve Martin! I love it's classic sob-fest sequence near the end where the baby is being born and Kate Bush's track This Woman's Work is playing underneath.
Here's a little montage of some of his films.