Additionally,
From
http://bartleby.com/
The common expression "a lot of" belongs to a class of words called complex modifiers, expressions like "a whole lot of" and "a great deal of".
Lot can occur with noncount nouns like furniture and with plural count nouns like chairs. The verb agrees in number with the noun in the of phrase. Thus, when followed by a singular noun, "a lot" of takes a singular verb:
EX: A lot of pizza was left on the table.
EX: A lot of food was eaten.
EX: There is a lot of milk.
But when followed by a plural noun, "a lot" takes a plural verb:
EX: A lot of the strawberries were ripe.
Lot has the further distinction of being used in the plural with similarly peculiar agreement rules. When followed by a singular noun, "lots of" takes a singular verb:
EX: Lots of pizza was left on the table.
When followed by a plural noun, "lots of" is plural:
EX: Lots of people were at the bookstore.
"a lot" and "lots" are also used as adverbs meaning “much” or “very much”:
EX: I’m feeling a lot.
EX: I'm feeling lots better.
Virtually all of the expressions discussed here have an informal tone, with the plural phrases like "lots" of having a decidedly more informal tone than the others.
alot. Teachers of writing have seen this form in student papers more times than they care to remember, and they can expect to keep on seeing it. Even experienced writers find themselves writing alot for a lot, especially when working under pressure or dashing off a note. The fusion of an article and a noun into a single word is a normal linguistic phenomenon, having occurred in another and awhile, so it is very possible that we all may write alot one day. For the time being, however, keep in mind that alot is still considered an error in print, so don’t be surprised if writing teachers and copy editors keep prying it apart.