This blog post is meant to accompany my video here.
These are plans for a bathroom shelf, with a toilet paper holder on the left side, three shelves for storing things, and a towel bar.
Your available space will dictate what sizes you can make the shelf, but I built mine four feet tall and a little over two feet wide. The back board is made out of six three foot 1x4s and one thirty-eight inch 1x4. The boards are each placed two inches higher than the board to the left.
The boards for the sides are all 1x6s 36", 30" and 28" from left to right. A 24" 1x6 is placed flush with the top of the left side and serves as the front of the channel, and keeps the toilet paper in place. You could fancy things up, and create a slot in the 1x6 so you can see how many rolls are in the channel.
The shelves are placed to line up with the boards on the back, with the exception of the lowest shelf, as it obviously is below the lowest board on the back. I placed this about eight inches lower than the shelf above it. I planned on using that shelf to hold extra towels, so I figured I'd need a little extra space there.
The towel rod was suppose to be a large dowel, but I ended up deviating from the plan with a 1x2. Figure the position carefully, take into account the mounting location, the height of the toilet, if you are mounting this above a toilet, and how far the towel will hang down, and position the bar accordingly. You could either drill holes in the two side boards and glue the bar in, or create two brackets to hold it, it's up to you.