
Rental bathrooms are often small, a fact that can make storage options tricky, especially when coupled with landlord restrictions. Here are twelve options, large and small, that make the most of vertical space, narrow floor space, and visual space.

1. Lipper International Bamboo Over-the-Sink Shelf, Target, $22.39: If you don't have much counter space, this over-the-sink-shelf can add some much-needed surface area.
2. Over-the-Door Vanity Station, Urban Outfitters, $69: If you aren't allowed to put any holes in the wall, this over-the-door station can hold some of your toiletries, and there are added hooks for jewelry, hand towels, or even lightweight towels like peshtamals.
3. Array Yellow Bookcase, CB2, $189: This shelf keeps a thin profile, adds a burst of color, doesn't require any holes in the walls, and maximizes vertical space. It would be perfect for holding towels, linens, and clothing and pajamas.
4. Iron Spice Rack, The Container Store, $19.99: This rack can either be mounted, or it can sit on the counter, and it adds a bit of height to your storage options. This would be perfect for deodorants, perfumes, nail polish, or other toiletries.

1. Organize It All Metro 4-Tier Shelf, Amazon, $39.06: Clean, classic lines, and a small spatial footprint make this shelf a good option for small spaces.
2. InterDesign White Wire 3-Shelf Tower, Target, $26.99: This unit is freestanding and incredibly thin, which makes it a good candidate for that tricky narrow space between the toilet and the tub or the toilet and the counter.
3. Organize It All Metro 2-Tier Wall-Mounting Rack with Towel Bars, Amazon, $24.97: Shelves and towel space, all in one affordable package.
4. Format Storage Shelf, CB2, $69.95: This clear shelf takes up very little visual space but offers plenty of extra surface for your toiletries or other items. Clear jars with Q-tips and cotton balls would look fabulous on this shelf.
1. 6-Shelf Iron Folding Tower, The Container Store, $119: This shelf folds up, which makes it a cinch to take with you if you need to move. 2. Lillången Laundry Cabinet, IKEA, $129: This cabinet makes laundry sorting simple, and it makes the most of taller ceilings, which is always great for small rental bathrooms.
3. Hyllis Shelving Unit, IKEA, $14.99: The Hyllis is fairly narrow, so it won't protrude too much into the room, and it offers a ton of storage for a small price tag.
(Images: as credited above)

White Enamel Four-P...
Anything for inside a shower? The metal caddy we have is rusting.
I love closed shelving for the bathroom. There's so much random flotsam and jetsom that is stored in there. Bandaids, ointments and tinctures, grooming supplies, extra toilet paper, maybe cleaning supplies, among others. I suppose baskets are the way to go?
I have the Format CB2 shelf in the bathroom above the toilet. I love it - and it matches my Kartell Stark polycarbonate stool.
http://www.urbanoutfitters.com/urban/catalog/productdetail.jsp?id=15220387&parentid=A_FURN_BATH_ACC
This one is AWESOME. Each level can hold at least four regular bottles of shampoo, ours is divided one for husband, one for me, one for both. I've had it 4 or so years with no rust, just clean mildew off the bottom as needed (there's drainage, but my shower isn't well vented).
@Pi, I have the Umbra Bird Bath shower caddy and love it. My favorite thing is that it has holes on the ends to put shampoo bottles upside down, slots for razors and hangers for washcloths. It's bigger than most of these, so holds a ton of stuff. I've had it a couple of years and no rusting so far on the few metal parts. http://www.umbra.com/ustore/product/bird-bath-shower-caddy.store# They have a wooden one, similar, as well.
Yep! I second the recommendation.
I also have the UO over-the-door vanity station, and I haven't been nearly as impressed by it. You have to be so careful to balance everything on it.
Weird. For a small bathroom, I wouldn't consider any shelving "smart" that has to take up floor space. Smart storage solutions for a small bathroom would be anything you can mount to a wall, so open shelving, medicine cabinets and other wall cabinets and racks.
I have a 10-inch deep shelf above the door where I keep extra bathroom tissue, cleaning products and my hair dryer. That little shelf is a lifesaver! I ended up putting a small glass shelf in the shower as well since I was constantly knocking over shampoo and other products in my small shower. A caddy was just too bulky for us. I'd love to have some kind of cart or bin for extra towels but the only usable floor space in our bathroom is being used by the garbage can and a digital scale!
LA Lady --- these products are recommended for renters precisely because they don't require wall installation.
I have the iron spice rack from the Container Store in my kitchen, and I like it, but I wouldn't put it on a bathroom counter--it would definitely rust and make a mess. Hanging might be ok, but it strikes me as an odd suggestion for a bathroom.
Does anyone know of any corner shelving?
My bathroom has a corner glass shelf but I would like to get more out of that space, perhaps a piece that has two levels.
I have a small bathroom so I bought the Ikea Shelf in white that is pictured in #3. It was the best decision I've made because it works so perfectly. One the last shelf I put a giant basket that holds all of my extra toiletries and it fits so perfectly that guest cannot see what is in it.