Keeping track of all this IT crap

[Ben Scott]

  I may have asked this here before, but if so, I seem to recall there
wasn't a good answer at the time.  Or maybe I just forgot and can't
find it in the archives.  Either way, worth asking again.

  Do people know of any good software to keep track of all this IT
crap?  Users, computers (with make, model, serial, CPU, RAM, etc.),
patch panels and their jacks, switches and their ports.  Most
importantly, what is connected to what: User A has computer B plugged
into jack C which is patched into port D of switch E.  Multiple times
100 users, two buildings, and eight switches, and damn things are
confusing.

  I'm looking for FOSS so I can (1) be cheap and (2) extend it to do
what it doesn't.

-- Ben