Based on the Marvel Previews #81, May for July 2010, I'd say you need to pre-order the following books in order to keep up with Spider-Man.
Core Titles
Amazing Spider-Man #637, cover by Coipel
Amazing Spider-Man #637, cover by Mike Flyes
Amazing Spider-Man #638, cover by Quesada
Amazing Spider-Man #638, cover by Rivera
Amazing Spider-Man #639, cover by Quesada
Amazing Spider-Man #639, cover by Rivera
Astonishing Spider-Man / Wolverine #2
Peter Parker #5
Spectacular Spider-Girl #3
Spider-Man / Fantastic Four #1
Spider-Man, Marvel Adventures #4
Ultimate Spider-Man #12
Web Of Spider-Man #10
World War Hulks: Spider-Man Vs. Thor #1
World War Hulks: Spider-Man Vs. Thor #2
Guest Apps
Amazing Spider-Man Presents: American Son #3
Amazing Spider-Man Presents: Black Cat #2
Avengers #3
Avengers #3, variant cover
Avengers: The Children's Crusade #1
Avengers: The Children's Crusade #1, Women Of Marvel variant cover
Shadowland #1
Shadowland #1, wraparound variant cover
Ultimate Mystery #1
Ultimate Mystery #1, villain variant
Ultimatum HC, Madureira cover HC
Ultimatum HC, Turner cover HC
Wolverine Weapon X #15
X-Men Forever 2 #3
Reprints
Amazing Spider-Man By JMS Ultimate Collection Book 4 TPB
Amazing Spider-Man: Official Index To The Marvel Universe TPB
Essential Defenders Vol. 5 TPB
Marvel Universe: The End Premiere HC
Marvel Universe: The End Premiere HC, variant edition
Siege: Battlefield Premiere HC
Spider-Man Magazine #12
Spider-Man: The Gauntlet Vol. 1 - Electro & Sandman TPB
Spider-Man: The Gauntlet Vol. 4 - Juggernaut Premiere HC
Women Of Marvel: Celebration Seven Decades TPB