Online Lens Simulators

what kind of lens do you need? Wide angle? Telephoto, Portrait Macro?

Canon

http://cusa.canonlenses.ca/lens-tester?LensID=30&CategoryID=6&leftLensID=49&rightLensID=30

Nikon

http://imaging.nikon.com/lineup/lens/simulator/

A bokeh simulator & depth of field calculator by Michael Bemowski

http://dofsimulator.net/en/