a lot of

lots of

There is not much difference between a lot of and lots of: they are both used mainly before singular uncountable and plural nouns, and before pronouns. It is the subject, and not the form lot/lots, that makes a following verb singular or plural. So when a lot of is used before a plural subject, the verb is plural; when lots of is used before a singular subject, the verb is singular.**

A lot of time is needed to learn a language.

Lots of patience is needed, too.

Lots of children prefer McDonalds to Burger King.

A large amount of

A great deal of

A (large) number of

The number of

These are used in similar ways to a lot of and lots of, but are more formal.

A large amount of and a great deal of are generally used with uncountable nouns.

A (large) number of is used before a plural noun and requires a plural verb.

The number of is followed by a plural noun and requires a singular verb.

I �ve thrown out a large amount of old clothing.

A large number of problems still have to be solved.

A number of people come to the festival every year.

The number of people who eat liver pate is actually quite small.

There is/there are

When using these structures, the verb agrees with the noun following it.

However in informal English, there �s is possible with a compound or plural subject.

There are many people in my class from Thailand.

There is an interesting statue of a troll under Aurora Bridge.

There are a gun and a knife in his bag.

There �s a gun and a knife in her bag.

?There �s a lot of weeds in my garden.