NBAdraft.net gives you a mock draft based on the inverted standings all season long. Their whole mock draft is based on a order that probably would come to reality. They're slotting guys in at places based on team need and player talent and so it's not ranking the players from best to worst.
DraftExpress.com gives you a prospect ranking for most of the year. They're ranking from best to worst in their opinion. They offer mock good mock drafts leading up close to the draft. Because of this I personally feel they are the better product. Opinion stops at talent evaluation and doesn't include who might be drafting where.