I'll throw my 2 cents in...
spyware is legal, thats why companies that make it don't get shut down by the authorities. Terms & conditions somewhere usually spell it out in fine print (you actually agree to it, but other things you DONT agree to in some way, shape, or form, are illegal, ie. viruses/trojans/worms). The FBI will go after virus writers, but not spyware writers for those reasons.
If you truely want to get some of the biggest pain in the **** spyware on a machine, download spywareblaster on a clean machine and note some of the more recent URLs in there database of 3500+ urls. then visist those sites with your test machine and install their... toolbars, programs, etc.. and reboot, (plus, surfing the sites Buzz told you will get it pretty good as well). Have fun!, I run a test machine my self and do the same thing.