Since the question as it is written asks for speed, one of the devices mentioned above will definitely fit that bill.  Especially if you are processing a large amount of citrus.  Me personally, I'm not a huge fan of uni-taskers in the kitchen.  Thus, I generally opt to: 

 * Roll the fruit in all directions while still whole. Apply a decent amount of pressure.  
 * Halve the fruit  
 * Squeeze the fruit into your container, you can use a mesh strainer to catch seeds and  large amounts of pulp  
 * You can use this method in conjunction with a sturdy fork pressing into the fruit against the palm of your hand to extract as much juice as possible.

Mesh strainer -- http://www.amazon.com/Norpro-KRONA-Stainless-Steel-Strainer/dp/B00004RDE1