Something I believe peope should study more is the master of photography, or arthistory in general. I can’t say I’m an expert on the history of photography myself, but I have an interest and have studied arthistory as a student, which included some photography. Get inspiration from the Internet:

• The user PhotographyMasters has a lot of interesting things to look at.
• Rangefindergeneral has a film on Diane Arbus.
• If you feel a need for a timeline Photo.net has one
• Robert Leggat has made site with information about early photography
• And there’s always the linklist from Witcombe, a resource I used a long time
• You might also find a lot of places who sell prints and stuff, like

If you have tips, please post a comment with the link :)