So, I use rxvt as my daily interface to my computers. I also use mutt for my email reading pleasure. Sometimes, I get URLs in email and I want to read them in a browser. If I was using a GUI based mail reader, I would just click the URL to open it. Well, there is an easy way to set up rxvt to do that!
URxvt.perl-ext-common: default,matcher URxvt.url-launcher: /usr/bin/firefox URxvt.matcher.button: 1
And either do a xrdb --merge ~/.Xdefaults or log out/log in. And start a new rxvt, and you are good to go.