Paper dimensions
http://www.printernational.org/american-paper-sizes.php
Color Modes
http://www.printernational.org/rgb-versus-cmyk.php
Where to find new brushes
http://browse.deviantart.com/resources/applications/psbrushes/
http://www.brusheezy.com/

http://www.photoshoproadmap.com/Photoshop-blog/2007/10/25/100-awesome-high-resolution-photoshop-brushes/
http://brushes.deviantart.com/journal/3939334/
How to install brushes
For windows
Place the *.abr files into:
Program Files\Adobe\Adobe Photoshop X\Presets\Brushes where X is the version number for your version of Photoshop.
For Mac
Hold the Command (Apple) key and click on the Photoshop icon (or Illustrator, etc.) from the dock. You will be instantly taken to the [...]