Normally, you have to choose one of those smilies from the site and an address is displayed at the bottom of the page (or top, depends) this you copy and insert in your text. make sure that these " [IMG]" are around the image address. Depending on your browser, you can also right-click on the image and choose copy image address in the appearing menu.
And again, a german site. It has very many smilies, and really big ones too. http://www.world-of-smilies.de/ but their code is a bit strange, you have ot cut away everything that is outside the brackets.
This one just: Please Register or Log in to view the hidden image! bet you cant get shorter than that.... unless youve got a smilie of neo, then thatd be: this One: Please Register or Log in to view the hidden image! Please Register or Log in to view the hidden image! heyhey. beat that.