Here's one to identify, found in a heavily grazed horse field. On it own. No distinctive smell. No staining when bruised/cut. Smooth slightly shiny skin almost like egg shell. Stalk wet when sliced in two.
My encyclopedia would indicate volvariella volvacea as a likely candidate - straw mushroom. But that is just a guess - there are a lot of these models that do look alike
-Emile
I reckon its Volvariella speciosa.
http://www.rogersmushrooms.com/gallery/DisplayBlock~bid~6915~source~gallerychooserresult.asp