I was inspired by the j1studio T-shelves a while ago- I prototyped them in paper first poorly then much more accurately. I highly recommend trying the second iteration yourself before you start on the rather more expensive wooden version of these shelves. It's also much, much easier to make these in paper than in plywood (you can act like it's 2D). But I needed to take this all the way and copycat properly.

So here's my take on the t-shelves. Beautiful, modal, furniture. It's flat until you set it up; when installed with easy slotting and zip ties to make it permanent, it looks like sculpture. Kind of like grown-up, useful Legos.

In case you'd rather just buy a set, here's the original: http://www.j1studio.com/furniture/tshelf/
It's a little on the pricey side, but very professional.

Step 1: Materials

Materials:

Plywood (one 4"x8" 1/2" piece makes 16 of the basic triangles).
Some 1/4" plywood to lasercut a pattern (or make the pattern some other way)
Zip ties in the amount of about 32 per sheet of plywood (stainless steel ones look really classy)
Something to treat the wood
Fairly substantial scrap wood to make jig and sled, and some screws and nails

Tools:

Router and tips:
- 1/2" tip with bearing at the top (to ride in the pattern and rout out the slots)
- 45 degree angle (to bevel the edges)
Table Saw
Safety equipment (eye protection, hearing protection, breathing mask)
Sander
Circular saw
Laser cutter or an alternative (for making the pattern)

Step 2: Cut a Template

I would have uploaded an inkscape file of the pattern you'll need to make for the router, but mine was wrong anyway. Do careful math and make a nice router pattern.

Step 3: Cut Down Plywood

On the table saw:
Rough cut the 4'x8' sheet of 1/2" plywood in half to make 4' squares.
Make exact 23 3/4" squares, making sure to cut on every edge so that none of the original cuts (we can't trust the cuts on stock plywood) remain.

Step 4: Make a Sled

Using scrap wood, make a sled to cut the triangles.
Line up one of your squares so that one diagonal is exactly on the edge of the scrap plywood. Trace the triangle onto the wood and cut it out, offset inward, with the circular saw. This should now fit a square of wood, so that the diagonal is pushed out a bit to let the table saw run it through.

This really is good enough to cut on the table saw. But if you want to make it easier on yourself, mount it on a bigger piece of scrap plywood and mount as shown. Connect the two ends (where the saw won't go through) with stabilizing pieces of wood as shown.
Place your square into the jig and add some straight bits of wood to the un-jigged side so you will be able to drop in pieces of square wood.

Step 5: Cut Triangles

Raise the blade of the table saw up through the sled.

For each square:
Drop square into sled. Cut down the center with a table saw.

Step 6: Rout Slots

You'll want to make another jig to hold your pattern on top of a triangle.

Drop in your triangle, then the pattern on top, and clamp in place. Rout slots.

Step 7: Bevel Edges

In order for the shelves to fit together properly, use the 45-degree router to create beveled 45-degree angles on the legs of the triangle. The bevels should meet at a point in the center of the thickness of the plywood.

Don't bevel the hypotenuse- it's not necessary.

Step 8: Sand

Sand everything so that it's nice and smooth. You can use a power circular sander on the flat bits.

Don't sand through the top layer of the plywood!

Step 9: Drill Holes

You need a hole in the acute corners of every triangle and two in the corner of the right angle.
(If this makes more sense: say you left the whole thing square. Drill two holes in each of the corners, which should mirror across the diagonals. The smaller triangles are what you get if you cut along the diagonals.)
Drill to a size that fits the zip tie, then countersink.

Step 10: Finish

Do any more sanding you feel is necessary.

Paint on finishing treatment.

Step 11: Assemble!

Slot your pieces together! It's really fun.
For inspiration, check out the designer's site: http://www.j1studio.com/furniture/tshelf/

Step 12: Zip Tie

Zip tie pieces together through the holes in the corner.
Also check out, on the designer's website, the idea of suspending shelves through the holes with steel cables instead of zipties. Cool!

Step 13: Finished Pieces

Your shelves can look good in any number of configurations. Here's how I set mine up!

(Dorm life is pretty rough, right?)

The gallery of the j1 studio site has a lot of other, more complicated configurations too.