On all the browsers on my Mac, if I want to go to a www.some_website.com address, I just type some_website into the location field. Recently I discovered that if I want to go to a sub-section of a website, I can type some_website/subsection. As far as I can tell, this doesn't work in Internet Explorer for Windows.
[robg adds: I couldn't get this to work in Firefox (2.0.0.4), but it did work in Camino, Safari, OmniWeb and Opera.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20070727081325187