Well, sadly, there aren't many "free" plugins out there that are worth downloading. Don't get me wrong, there are some but none that will do anything more than what CEP 2.0/AA can do already. If you're looking for plugins for synths, there are a lot out there but most are trials that have limited functionality or will quit on you after 30 days. If you want to see what the WWW has to offer, perform a search with Google and see what you get.
So, I guess you really only have 3 options... Fork out the dough for the full products, download crap or make use of what you've got. And honestly, the last option is probably your best choice. Also, you may want to consider upgrading to AA 1.5. It has basically the same architecture of CEP 2.0 but it has some enhancements that will make any CEP user happy. There are a few cool new effects, too!
And one last piece of advice... Stay away from Limewire and other P2P networks. Many of those files contain viruses and other such malware and if you're not careful, you'll destroy the computer that houses all of your audio creations.
P.S. - If you don't mind paying for your plugins, check out
IK Multimedia