The haiku is probably the most concise form of poetry that is taken seriously. Of course, that doesn't mean that I'm one to take it all that seriously...

Here are some of my more, shall we say, "inventive" haikus:

Three-Word Haiku
C++ Programmer's Haiku
volatile true friend,
register for union class.
for this, do double.
Failed Romantic Haiku
I wanted to write
A haiku for you, but I
Ran out of syllab
The meta-Haiku
An observation:
Haikus are concise, but they
Don't always say much.
dot dot dot dot, dot
dash, dot dot, dash dot dash, dot
dot dash, dot dot dot
Religious Haiku
And yea the Lord spoke,
Saying, "Let there be haikus."
And there were haikus.