Of the quarter of a million words in the OED [Oxford English Dictionary], about half are nouns, 25 per cent adjectives, 15 per cent verbs and the last 10 per cent are prepositions, conjunctions, suffixes etcetera. It is this last category that yields most of the top 10 most frequently used English words, according to a 2006 survey carried out by the Oxford English Corpus. They are: the, be, to, of, and, a, in, that, have and I. The 10 most popular nouns were: time, person, year, way, day, thing, man, world, life and hand. The 10 most popular verbs were: be, have, do, eat, sleep, drink, put, keep, run and walk. The 10 most popular adjectives: good, first, new, last, long, great, little, own, other and old.I am kind of surprised about hand and run and walk. Considering the source is the Oxford English Corpus -- which comes from literary textual sources, not the spoken word -- I suppose it does make sense.
P.S. While I am loathe to cite a Wikipedia article about anything, there is an interesting entry for Stephen Fry (at least as of 25 February 2010 at 10:04 p.m. EST).