In the Terminal, type "open http://www.apple.com" and your default browser will launch and open this page. I think this is only possible in 10.2!
[Editor's note: I don't think this worked in 10.1, either (at least not according to this hint). Run "man open" for some other possibilities.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020902074127468