Technosphere, at http://technosphere.org.uk, is/was sort of a forerunner of NeoPets, allowing you to make a cute cyberpet which you can then watch as it plays out its virtual life: eating, moving, reproducing, and eventually dying. You have to check up on them at the website to get the full entertainment value, but if you can't be bothered they'll write you e-mail to tell you what's been going on.