Is there a site someplace that lists the contents of
/proc and what each entry means?
The documentation for Linux's implementation of
/proc is in
Documentation/filesystems/proc.txt in the kernel documentation.
/proc is one of the areas where *ixes differ most. It started out as a System V specific feature, was then greatly extended by Linux, and is now in the process of being deprecated by things like
/sys. The BSDs — including OS X — haven't adopted it at all. Therefore, if you write a program or script that accesses things in
/proc, there is a good chance it won't work on other *ixes.
Yes, there is a man page in section 5 "File formats and conventions":
It is surprisingly long, though - it describes 189 kinds of files in
/proc has the files that are stored on RAM when the system boots and remains there as long as the system is up. Getting to know what's in this file is like reading RAM. That's why you can't change the contents or values of these files using vim or some any other editor. They need to be forced with some boolean values.
Here I've got some good documentation with the whole list and descriptions of each item.