I dumpster dived a wonderful desk and refinished it. Would like to put a piece of glass on the top to protect the finish and make it  smooth and easy to clean.I was thinking of salvaging glass from a storm door. Is the glass in a storm door suitable for a desk top? Any hints on how to make a clean cut to fit the desk. Lastly how to I treat the edges so I do not get cut when rubbing against it ?

Well I make windows for a living, and we use 1/4 inch plate for the desk's around the office. as for the edges, we use a belt sander on that.

A storm door should be tempered and you won't cut that.

Call a glass shop-for this. A 1/4 inch plate sanded-shouldn,t be over 30 bucks

You can also maybe try going to Lowes/Home Depot and they can usually cut the glass to your size you need.  

One other thing to keep in mind - put a penny or some other such object at all four corners of the glass when placing it on the desk top - this will keep moisture from building up underneath.