Yes, OnDeckBaseball, referred to in the above post, has done a Top 500 for at least the past 2 years. But this site hasnt posted an entry in almost 3 months, so I dont know if he'll be doing a list this year, or if he does it may be too late for your drafts.
Rotoworld does a Top 150 list every year, and Scout.com did one last year, so that's a little deeper anyway. But you can get some 'deeper' prospects by looking at BA's League Top 20's and Team Top 10's. The scouting rpts are subscriber content, but the lists themselves are not.