Best Of

I guess the only thing I would add is that the strong light should be a daylight bulb 5000k - 6500k.  Yellow light, say 2500k, is not great for studying posters and taking photos.  You can buy 400 Watt equivalent compact fluorescents that rate ~100-110 watts for about $20...  You can spend more for bigger photo bulbs.  My bulbs are about 10” long.

I'm mostly a lobby card guy, so I have a few other items in my basic toolkit.  All specifically for lobbies.

A B size 14x17" flatbed scanner.is better than a camera for capturing lobby card images.  Very detailed and easy to adjust images.  Wouldn't give it up.

In addition to the Bestine, I keep an art-gum eraser and a dry cleaning pad to remove surface dirt.  A small amount of effort makes a big difference in the card's appearance.

Bags Unlimited 2 mil poly lobby card sleeves.  These have a sealing lip and will hold a set of 8 cards.

Tubs that store the cards vertical.  I use a layer of foamboard on the bottom to avoid denting and also have stiff boards in the back and in a few places in the bundle to prevent bending of the cards.  Index dividers would be good, if I ever get around to it.  

Other cleaning supplies for de-acidification, bleaching and cleaning.  Also a baking sheet with a lip on the edges to hold solution.  I am still in the process of learning to clean cards, and the subject is way too complex for this thread.  This allows me to buy cards in lesser condition and have a shot at improving them.

Bunch of glass pieces to flatten the posters?

Just to add to what else I have..

A tape measure is a must, I use a fabric one like for sewing as theres less chance of damaging the paper.
Also a Black light is essential for checking restoration , I have a mains one, and two small torches, you'll be amazed what they pickup. I take the torches if I'm viewing one at another place.
I have a 250 piece Water colour pencil set, for the odd basic touch up, you'll be amazed how much better something looks with minor work.
I also have magnifying glasses, with lights on, great for looking at fine details, and also for using when touching up posters.

Lots of other stuff, but I think these are basics, with what Bruce and everyone has posted so far..