I'm taking the same approach as the DC overview on the van. Below the cut are the categories I'm currently thinking are the most popular.
Marvel Comic Universe
This is not a definitive list, but an overview of the most popular characters and 'ships.
Iron Man/Tony Stark
Captain America/Steve Rogers (currently deceased)
War Machine/James Rhodes
Mary Jane (MJ) Watson
Green Goblin/Norman Osborn/Harry Osborn
Doc Octopus/Otto Octavius
Aunt May Parker
J. Jonah Jameson (Daily Bugle)
Professor Charles Xavier
S.H.I.E.L.D (Supreme Headquarters International Espionage Law-enforcement Division)
Superhuman Registration Act
Tony Stark/Steve Rogers
Tony Stark/Pepper Potts
Peter Parker/Harry Osborn
Online Fandom Resources
Some useful resources:
Overview by elspethdixon
Newbie Guide to Iron Man by likeadeuce
All of this is very preliminary, and I'm sure it will change over the next couple of week.
Please do get involved! Marvel is huge, and I can't possibly do it justice on my own.