www.plugins.com - Offers a list of plugins for Photoshop and Paintshop Pro.  

www.netins.net/showcase/wolf359/plugcomm.htm - A great site for info on plugins and Photoshop.  

www.digieffects.com/ - DigiEffects are the makers of Aged Film and other special plugins.  

www.multimedia-lab.com/ - They make video plugins/optimizers and a 3D painting plugin for Photoshop.  

members.aol.com/dgdominion/index2.html - Digital Dominion has made a Photoshop plugin called Cinematte for bluescreen compositing.  

www.ulead.com - Another Photoshop Plugin company with a wide variety of useful plugins.