Based on the Marvel Previews #68, June for August 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 #601
Amazing Spider-Man #601, 70th frame variant
Amazing Spider-Man #602
Amazing Spider-Man #602, 70th frame variant
Amazing Spider-Man #603
Amazing Spider-Man #603, 70th frame variant
Marvel Adventures Avengers #39
Marvel Adventures Spider-Man #54
Mary Jane And Friends Posterbook
New Avengers #56
New Avengers #56, 70th frame variant
Ultimate Comics Spider-Man #1
Ultimate Comics Spider-Man #1, special variant
Ultimate Comics Spider-Man #1, villain variant
Guest Apps
Dark Reign: Mister Negative #3
Dark Reign: The Sinister Spider-Man #3
Official Index To The Marvel Universe #8
Timestorm 2009/2099 #4
Reprints
Essential Marvel Team-Up Vol. 3 TPB
Marvel Adventures Spider-Man Vol. 13: Animal Attack Digest TPB
Marvel Bromance TPB
Marvel Masterworks: Deathlok Vol. 1 HC
Marvel Masterworks: Deathlok Vol. 1 HC, variant edition
Secret Invasion Chronicles #6
Spider-Man/Mary Jane: ... You Just Hit The Jackpot TPB
Spider-Man: 24/7 Premiere HC