Well, I've only thought of it since reading Drodrig's post, so give me a moment or two! LOL!!
Okay, sizes are based on my existing bookcase, so this will need to be adjusted to fit each person's own space.
My bookcase is 34 5/8" w x 72" h x 10 1/2" d (though that's not important!). A comfortable working height for me is 28". I'm going to use 1/2" MDF board for the top as it's smooth, and moisture will not be a concern, neither will how the edges look. If you need this to also look good, then you'll have to find the appropriate edging for your taste!
I figure I'll need:
TOP: MDF 1/2" x 34 5/8"x44"
LEGS: 2 x 1/2" x 27 1/2" 5/4 pine (I'll taper them down to 2" w at the bottom starting 4" from the top)
LEG CROSSPIECE: 2 x 1/2" x 26 5/8" 5/4 pine, this will have the legs screwed on with a full overlap joint. It will also be the piece that will have the hinges attached.
TABLE CROSSPIECE: 1 x 1/2"x34 5/8" 5/4 pine that will be hinged to the shelf and attached to that end of the table top.
HINGES: 4 hinges, cheap hinges I figure 4" x 2" will do the trick
SCREWS: 8 x 1 particle board ones, about 30 of them, 4 each per leg, 6 each per hinge and the balance to attach the top to the top cross piece. These were scientifically chosen based on me already having a box of them!
The leg assembly (http://i2.photobucket.com/albums/y16/astr8shooter/Legdetail.jpg) will obviously need to attach at the appropriate spot for a level table top!
I've left over scrap plywood for the legs and crosspieces, so I only need to buy the MDF and the hinges. I've even have some left over paint to cover up the raw materials. Now to build it!
edit I decided the plywood would be too flimsy for legs. I have some 5/4 pine boards that will do much better! /edit