Hydraulic symbols for drawing schematics

http://www.wikiplc.com/index.php?option=com_content&task=view&id=31&Itemid=31

also, hydraulic forumlas: http://www.hydraulic-systems.com/pages/ref_formulas.htm
also, Introduction to Fluid Power: http://www.tpub.com/content/engine/14105/

also, MTH (austrian hobby hydraulics maker): http://www.modelltechnik.at/eindex.htm