The Money Pit. Old 80's with Shelly Long and Tom Hanks. It's without doubt the funniest film I've ever seen. Closely followed by the National Lampoon films.
Have you seen Achmed The Dead Terroris clip on you tube? If you found that funny Jeff has 2 of his full shows on watch-movies.net, which you can watch for free. And yeah it's proper laugh-out-loud kinda stuff.
Bruce Almighty is funny
The Break Up
Mrs Doubtfire
Terms of Endearment ( also very sad though in parts)
I love all of these - make me laugh every time.