How do you plan to cover it? If you want it to be a show piece you need to use the good Birch or hardwood Plywood. A 4x8 sheet of 3/4 plywood weight in at ~75 lbs. Not light.
Lowes has 3 or 4 different grades of plywood
Construction grade, Good for roof and walls.
Cabinet grade, Good for cabinets, Pine that is sanded on one side.
Cabinet grade, Birch, For really nice Cabinets
And i think the had a Hard wood that was expensive. Might have been oak.
I'm useing the pine, Cabinet grade plywood. I haven't done much wood work in the last 23 years so I didn't want to use anything too expensive. I plan to cover it in carpet so It doesn't need to be pretty.
I'm building mine into a sleeping platform so I need it too hold my weight. I went with 3/4 for the top and side and using 1/2 for the drawers and bottom.
If you have time to learn 3D cad it will help you make fewer mistakes, I'm using FREE google sketchup. It really works great for this kind of project. I learned enough in 2 or 3 days to draw up my drawers.
A link to my build is in my sig,