In your investigations you may want to consider a thing called "air over oil". This way you don't need a hydraulic pump and all the other equipment. If you already have pneumatics on whatever you are building and only need 1 or 2 motions then air-over-oil may sound like the better option.
Here are some animations
In this one the cylinder on the left could be a pneumatic cylinder with air on top, or a pressure reservoir with air pressing directly on the fluid.
http://travel.howstuffworks.com/animation31.htm
Here is another variant.
http://www.airhydraulics.com/Product.../Animation.htm