If you are a writer, the Absolute Write forums are worth a look. I have been visiting almost daily for many years now and am now also a moderator for the erotica and non-fiction subforums. I bring this up today because I am continuing a blog chain by a number of forum members. The post immediately before mine is Testing the Funny at Polenth's Quill.
My own approach to humor is a cautious one. After being encouraged by my editor at Loose Id I attempted to add some humor to my writing in the story Tongue Tied. To this day I find it hard to gauge how the book was received. Some found it to be extremely funny, others don't comment much on that aspect.
People seem to vary a lot in what seems funny to them. I personally don't find kids that funny (sorry, and again), spam just irritates me, physical or broad humor doesn't normal work for me--I experience any sense of embarrassment, even in sympathy with a fictional char cater, far too acutely to really enjoy the humor in most cases. But I do like absurdest and word play humor (think Eddie Izzard) and some elements of farce, and that was what I tried to work into my story.
But I also agree with the next post back in this chain that underneath the humor I like there is an element of exposing the truth of things. I have at least one planned sequel to Tongue Tied which is probably my most successful ebook so far in terms of initial sales. But until I get a better sense of how to write humor I am hesitant to start work on it.