You can buy plans, or get them free, but not as rewarding as doing your own. If you want to add to your WW'ing experience try laying it out.
Start with your needs. If you want legal size drawers, decide which way you want them...front to back or left to right. Measure the folders you'll be using, including a Pendaflex style (hanging), and include height for a tab.
The drawer size may determine width, depth, and height. Make allowances for spacing, drawer slides, ends/divider thickness, etc.
It's really very simple. Start off with a rough sketch and keep plugging in dimensions to the sketch to get final dimensions for the entire project.
Then you make a materials list, cut list, any fabrication details. Then cut out parts, put together, finish, and you're done. See how fast it really goes.
Or, you might try www.plansnow.com