The plugins that I find most useful and use on a regular basis are Alien Skin Eye Candy 5 and Xenofex 2. You can check them out at http://www.alienskin.com/
Another cool plugin is the Dreamsuite from Auto FX, http://www.autofx.com/
Check those out and see what you think, there are lots and lots more but these are my personal favs. :)