If you've been a good boy or girl, you've registered your game(s). Why would you want to do that, you say? Well, doing that gives you access to the Exchange where you can download sims, houses, and Maxis objects, as well as the forums and cool things such as mp3s and endings for your movies.
And what's with the MySim page? Well, if you create custom content (sims with blue hair and pink skin, houses) you can upload them to the exchange and they'll all show up in the Uploads section. You also have a blog, a guestbook, bookmarks, movies (if you upload some), and you get to create a really fun avatar.
biggrin If you're going to post a link to your MySim page, don't post
http://thesims2.ea.com/mysimpage/mysimpage.php. That'll take everyone to their own page. You have to click your avatar to get the right url.