This article is from the alt.usage.english FAQ, by Mark Israel email@example.com with numerous contributions by others.
With mass nouns, you have to use the singular. ("None of the
wheat is...") With count nouns, you can use either the singular or
the plural. ("None of the books is..." or "None of the books
are...") Usually, the plural sounds more natural, unless you're
trying to emphasize the idea of "not one", or if the words that
follow work better in the singular.
The fullest (prescriptive) treatment is in Eric Partridge's book
"Usage and Abusage" (Penguin, 1970, 0-14-051024-9). In the original
edition Partridge had prescribed the singular in certain cases, but
a rather long-winded letter from a correspondent persuaded him to