Voadam
Legend
SRD for looking up spells, monsters, and class abilities as needed.
Pictures pre selected for NPCs, Monsters, Items, Scenes, etc.
An electronic copy of the player's sheets so you can look up their stuff yourself.
I use www.invisiblecastle.com for online dice rolling.
If you have an electronic copy of your module being able to use a search function is useful.
PDF sourcebooks you plan on using are fine, but I wouldn't make them a high priority.
Pictures pre selected for NPCs, Monsters, Items, Scenes, etc.
An electronic copy of the player's sheets so you can look up their stuff yourself.
I use www.invisiblecastle.com for online dice rolling.
If you have an electronic copy of your module being able to use a search function is useful.
PDF sourcebooks you plan on using are fine, but I wouldn't make them a high priority.