Freemarters…. I’ve been keeping a database of plug-ins at Toolfarm, which is known as the Plug-in Finder. There is a very large section… make that the biggest resource of FREE AE plug-ins on the web.
Go to the Free After Effects Plug-ins page. Some of my faves are SuperPNG, Phillip Spoeth’s plug-ins and Sebastian Mecklenberg’s plug-ins, which you can’t get anymore unfortunately. There are lots listed here. Most are of limited use, but there are a couple of superstars here.