Assume that in the current buffer there is some text like
http://emacs.stackexchange.com/. Is it possible to customize Emacs so that double clicking on this text, results in visiting the link by the deafult browser? (i.e., like hyperref in LaTeX).
ffap RET does what you want (will be requested a confirmation though). You can bind it to double mouse click with
(global-set-key [double-mouse-1] 'ffap)
As the name suggests,
ffap finds files at point, not just URLs. If you want a function tailored to URLs look at the builtin
browse-url package (as suggested by Dan), which also lets you choose the browser to use. If you prefer
browse-url-at-point if you don't want to be prompted for confirmation, thanks glucas!) in the previous code to bind it to double click event.