There are many, many words in English that can mean "a lot".

 - abundance
 - bundles/bundle
 - collection
 - cornucopia (perhaps a stretch)
 - clump (sure, why not?)
 - conglomeration
 - glut
 - gobs/gob
 - great deal
 - heap/heaps
 - hill
 - hoard
 - load
 - many/much
 - mass
 - mountains/mountain
 - multitude
 - oodles/ (or less common) oodle 
 - peck
 - piles/pile
 - plenitude
 - plenty of
 - plethora
 - profusion
 - reams/ream
 - scads/ (or less common) scad
 - slew
 - spate
 - stacks/stack
 - superfluity
 - surfeit
 - surplus
 - tons/ton
 - whole lotta (slang, when spoken a certain way will mean *more* than just "a whole lot of")

Plus probably many more! Note that most of these will take an indefinite article as in "an abundance", but no article is used for plurals.

Many of these can also be intensified with a synonym of *large*, plus this allows for and additional words. Some exampless:

 - enormous amount
 - gigantic quantity
 - gargantuan pile
 - ___ of Herculean proportions
 - truly Brobdingnagian ___
 - large multitude

Not all of the words in the first list work well with the "large" prefix--I wouldn't say "a huge plethora" or "a giant ton".

In general, when used with *large*, a plural word becomes more literal and seems to refer to many separate groups of items instead of one group. That is, "heaps of dirt" doesn't necessarily mean individual masses as it can be used figuratively to simply mean "a lot", however "giant heaps of dirt" more strongly suggests individual, separate masses.