Based on the Marvel Previews #67, May for July 2009, I'd say you need to pre-order the following books in order to keep up with Spider-Man.
Core Titles
Amazing Spider-Man #599
Amazing Spider-Man #599, 70s decade variant cover
Amazing Spider-Man #600, 50/50 cover Alex Ross
Amazing Spider-Man #600, 50/50 cover John Romita JR
Amazing Spider-Man #600, variant cover Joe Quesada
Amazing Spider-Man #600, variant cover John Romita
Amazing Spider-Man Annual #36
Amazing Spider-Man Family #8
Marvel Adventures Avengers #38
Marvel Adventures Spider-Man #53
New Avengers #55
Ultimatum: Spider-Man Requiem #2
Guest Apps
Dark Reign: Mister Negative #2
Dark Reign: The Sinister Spider-Man #2
Deadpool: Suicide Kings #4
Marvel Adventures Super Heroes #13
Official Index To The Marvel Universe #7
Timestorm 2099/2099 #3
Reprints
Amazing Spider-Man By JMS Ultimate Collection Book 1 TPB
Dark Reign: The Goblin Legacy
Essential Peter Parker, The Spectacular Spider-Man Vol. 4 TPB
Marvel 70th Anniversary TPB
Secret Invasion Chronicles 5
Spider-Girl Vol. 11: Marked For Death Digest TPB
Spider-Man Magazine #7
Spider-Man Newspaper Strips HC
Spider-Man: Crime And Punisher TPB
Spider-Man: Family Ties TPB
Spider-Man: Spider-Man And The Human Torch HC
Ultimate Spider-Man Vol. 1: Power & Responsibility (New Printing) TPB