Robin Good: If you are looking for professionally-looking templates for POwerPoint, I suggest you to give a look to the dedicated search engine section on Slideworld: http://www.slideworld.com/ppt_templates/powerpoint-templates.aspx
Here you can find a wide variety of professionally designed PowerPoint templates / slides that can be purchased online and then edited and personalized on your computer.
More info: http://www.slideworld.com/
(Thanks to Baiba Svenca for having uncovered this)
Via Robin Good, Informatics, Lisa Durff