These are relay connections and clearly you have relays missing. although the brown one you are holding does not look like a relay terminal. Best thing to do is use the user manual in the useful thread section as this has a full wiring diagram for the whole car and from that you can determine what they are for. Also something else that would be good to do is to test all your electrical stuff is working on the car such as lights, indicators, electric windows, mirrors etc.
I know from when working on my car in that area that there are about 6 or 7 relays down there for different things. Actually scrap testing lights and indicators as these are found in the engine bay and under the steering column respectively. I believe those relays down there are for ignition, windows, fuel pump and a few other things but without checking the diagram again Im not 100% sure off the top of my head
http://forum.s15oc.com/announcement.php?f=39&a=1 then S15 service manual and it will be the section labelled EL for electrical
