That's so easy to do, too.
I wrote a Tourrettes syndrome generator about a year ago when I was bored at work one day. It's not as fancy as the site Anna mentioned above, but then it was only a quickie.
You can try it out if you like at www.infoxicated.com/tourettes.php
For best results, copy and paste something totally innocent, like an Ananova story or something. It's for over 18's only, really, as it does contain strong language.