Programmers are no strangers to strict requirements on form and syntax, so working in the poetic medium of the Haiku comes almost naturally.
Programming is fun.
Little virtual widgets.
Poems that do work.
The brevity and compactness of the haiku lends itself well to writing something tighly focused. I find them quite enjoyable to write.
Of course, there are quite a few other poetic structures of note which can offer a fun challenge. The limerick and the sonnet are two of my favorites. Here's a limerick I wrote (beware, obscure programming reference ahead).
There once was a coder named Chuck.
And through all the source code he snuck.
He changed not a line,
it all worked just fine:
he programmed by punching a duck!
A sonnet would be a bit ambitious for this late hour. So unleash your creativity, let's see what you've got.