This instructable shows all the materials, tools and steps I followed to make the bench, but it could all very easily be adapted to building other items. The bench used three interesting techniques that are worth mentioning here: Dove tails - they offer very high strength union for parts that are connecting at 90 degrees. Commonly used on drawers and chests, they can be made fully visible on both ends (like with this bench), or only visible on one end and not the other (I think that one is call a half dove tail). Mine were made entirely by hand, but if you're mass producing these things and looking for efficiency you should switch to using a router with a dove tail guide. Mortise and tenon - another high strength technique for attaching pieces. This was used for the quarter-round supports under the bench, and involve having one piece fit partially (but very tightly) into another. For the bench, the supports' entire top and side fit into the seat and leg (respectively) of the bench, and the union is practically invisible. Glue only. No nails or screws were used to assemble the top and the the legs it connects to. The adjustable legs on the outside of the bench are held on by simple bolts and wing nuts. The material of choice in this case is obviously wood. But there are several kinds, and choosing the right one depends on several factors like the wood's beauty, the cost, the ease of working it, etc.
In my case I knew I wanted to experiment with dove tails and mortise and tenon techniques, so I didn't want to buy really expensive woods only to see them get trashed. I ended up choosing pine to work with, and actually got lucky with the pricing too. It turns out that planks of pine that are knot free are more expensive (probably because that wood is stronger), but the knots are what would give the bench more character and beauty (in my opinion, at least), so the cheaper wood was actually exactly what I wanted. I ended up using two 8 foot lengths of 1"x10" (which cost about $12 each), but I think you could get all the material from just one board. I used two because I messed up one of the legs and also wanted more pieces with knots in them.
Once everything was finished I was able to stain and varnish the piece so the colouring can really be played with a bit at that point. The wood can probably be made to look like any type of wood (with the right type of stain), and the only thing to keep in mind after this is the softness of the material and how easily it can get scratched and dinged. Pine is a relatively soft type of wood (i.e. a 2x4 won't bend, but you can mark it with your fingernail), but given that this piece of furniture is going to be used by an 8 year old I figured it's going to happen anyway so there's no use using something really expensive.
As for tools, you need several clamps (especially tabletop clamps which will be useful when cutting the dove tails), a roughing planer, chisels, files, exacto knife, wood glue, jigsaw, regular saw and a coping saw. You will also find a mitre saw quite handy, as well as some sanding blocks, files, and the usual hand tools.