The sessions, opening and closing remarks, and show & tell will all require a projector. None of them will overlap, so you can get by with one, unless you're planning on having more than one session space.
Some venues have projectors, some don't, so best to research this ahead of time. If they don't have any, try asking local Ruby businesses if you can borrow theirs.
Ruby Australia has a collection of power cables and power boards that are shared from camp to camp. You should get in touch with the previous organisers to locate these and have them delivered to you.
This saves every camp from having to buy all of this gear again.
Ruby Australia has a dedicated Mac Mini for the purpose of hosting a RubyGems mirror and other such files and services at Rails Camps. Again, the previous organisers will be able to point you in the right direction and share details on what's needed to get it up-to-date.
Ruby Australia should be able to supply a wifi router (or routers) that will handle the networking traffic for the local network.
Not essential, but recommended: source a hundred or two pairs of earplugs, as most dorm rooms have a snorer present, and having something to help everyone else sleep is a nice touch. Sometimes sponsors have supplied these, and that's certainly a good option for them to win over attendees.