For a class (grad school), 76 pages of text (no graphics, charts, etc.) with another 18 pages of sources single-spaced. It was a lit review on the major hominid fossils from Africa that are more recent than .8 million years ago plus some analysis. It was surprisingly painless, as there is a lot of content to cover. Prof indicated he thought the paper was worth an A- but gave me an A because it contained not a single typo or grammatical mistake.
My personal favorite was the 8 page paper I wrote about a four line poem, though, that was the biggest load of BS I ever spewed. Stupid arts requirements.