newbie question about webpages

I don't want my site to end with .html or .php, how do I get the pages to end in a nice slash?

example: http://strobe.cc/quodlibot/

Your websever can respond however it wants to a particular request. That is to say that a url path doesn't have to correspond to a filesystem path. The short answer for apache is to use mod_rewrite, but you'd get the same effect by making websites like the grown ups do: with web frameworks.