Forum OpenACS Q&A: Shining examples
It's interesting to note that tomcat.org takes you to a non-descript French site, while slide.org ends up at some kind of Spanish ecommerce site. The point being, the name was chosen on it's qualities as a brand, not on the basis of an available domain name. Besides, if people don't know the URL, they'll use Google. You just need to make sure the brand itself is easy to spell and remember.
To bad Alexandria is taken ...