I should have added it ages ago but it took my son to remind me. Anyway, I have added a link to http://www.xkcd.com/ because I heartily recommend it. My particular favourites are 21, 138 and 571. To see these just add the number to the end of the URL so you get http://www.xkcd.com/21 for example. After looking at my recommendations just keep pressing the random button.