See this post at Balkinization.
Actually, I have been involved in a few instances in which forthcoming works were sent to all the Supreme Court justices for their information. For example, while Eldred v. Ashcroft was pending, the Loyola of Los Angeles Law Review put together a symposium on the case. Page proofs went to the Justices, and I believe at least one of those articles was cited (and presumably more of them read, at least by the clerk in each chambers assigned to the case).