How to ID electrical connections?

Looking around my jeep, I've found quite a few electrical plugs that are not being used. I would love to know what each of them is for. Is there a guide somewhere that ID's all of the wires or plugs on the jeep?

Here's a few I was looking at today, anyone know what these are?
(94 sport, stock. 4.0, AT)

Thanks!

By the ECU:



By the driver's right knee:



Behind the dashboard / by steering column:

First one is the ECU diagnostics port for a scanner.

a Factory Service Manual will have a full wiring diagram you can use to match wire color codes to figure out what the connector is. You can usually find them on ebay and from other vendors.

Alternatively, you can spend fifteen bucks on a Haynes or Chilton (etc) manual at AutoZone - they'll have a wiring diagram too, but the colors may be off or slightly modified as these manuals usually cover a far wider range of model years and things change occasionally.