One simple tip is to create and include a reference code within it, so that at when you get a call from a company or an agency, you'll know which CV they have and how they got it. It may not always be from where you expect.
For example: if you include "ref: M12-04" in your CV, it might well tell you (assuming you keep alog of them) that this CV was uploaded to Monster in April 2012.
The system is entirely up to you and can be as simple or complex as you like. You could include the code in the body of the CV or as part of the file name - Just remember that if you include it in the filename, don't hide your actual name in a jumble of letters and characters.