Wordpress have serve me quite a long time for my other website. I wrote a small blog post testimonial during the Unofficial WordPress Day of July 1st. Anyhow, I truely like this piece of software and releasing their official logo would actually promotes their brand more.
They have include various format for print, web, phone and vector image to accomodate your designing needs. If you intend to print them, they also have penton code to make sure the color is right.
There is even WordPress Wallpapers for your Desktop, iPhone and iPod.
Get WordPress Logo Here
i am looking on those full quality/ full resolution logo for all the open source software
i guess this will be a good start