To be truly and evilly pedantic, the following aren't really proper haiku. For one thing, proper haiku are written in Japanese. The English syllable is simply a somewhat different concept from the Japanese mora, which is the unit traditionally counted in haiku. Consequently, any English haiku is in some sense only an approximate haiku. Proper haiku should also contain seasonal references, which are not universally present here. (Here's an excellent reference on the history of the form, including some interesting discussion of options for adaptation into English.)
What I have to say about all that is this: Feh! It's good to know, but also terrific fun to just bang out little gems of five-seven-five formatted minimalism, so just pick some rules already and get to work! Of course, along the way one writes gobs of hopeless tripe like this:
Lions and tigers
And bears, oh my, oh no, oh
Damn, it doesn't fit
But what are you going to do? (Oddly enough, I've received several positive responses to that example of what to me was just another haiku miss, albeit a reasonably amusing one.) River of haiku / I dip in and grab a few / Here are some I like.
Never forget me
I will never forget you
(Whoever you are)
Rolled-up newspapers
Do not hit your dog with them
Spread them on the floor
A lump in the fire
Is it a piece of charcoal
Or a hamburger?
One two three four five
Six seven eight nine ten twelve
Who needs eleven?