One of my grammar books states that people who say “between you and I” commit an error of “unsurpassable grossness.”’
I think this statement is overkill. However, “between you and I” is an undeniable grammar error. “Between” is a preposition. The pronouns following must be in the objective form. Therefore, the correct answer — the only answer — is “between you and me.”
Watch for it over the next week. Between you and me, there are a number of people who don’t get it right.