Well, manuals I'm golden for. I keep all my manuals and they're are in fairly good condition. However game boxes, i.e., the old style cardboard ones, I've almost never kept (except for LoZ:OoT, but it had the spiffy "hologram" cover).
I can actually just list off boxes I do have, right now fairly quikly:
GBA:
Castlevania : AoS
DK King of Swing
Dr. Mario/Puzzle League
Kirby nightmare in Dream Land
Metroid Fusion
SNES:
Super Caslevania IV
Super Ghouls and Ghosts
Genesis:
Castlevania Bloodlines
Misc:
Black GBA SP
Hori Black GCN controller
Original PS2
GCN
Other than that, as I said I still have the manuals for waaaay more titles. The systems I own are:
Atari 2600
Colecovision
NES
Sega Master System
SNES
Genesis
Sega Saturn
Dreamcast
GB
GBA
GBA-SP
NDS
PS1
PS2
GCN
XBOX
and of course, a Wii (on Sunday).
So, I have at least a few games for all of those above mentioned systems.
The reason I mention this is because I don't have the time to just start scanning like crazy, however if there is a specific thread where you can view all unfilled requests (i.e. scans people actually would want and use) I'd be more than happy to scan in whatever anyone needs that I have. In short, I am more than willing to help, I just don't have much time to devote - so I'd like to keep it as streamlined as possible