Try allplatehangers.com. I bought mine to hang some tiles after reading this great post on AT.

http://www.apartmenttherapy.com/boston/how-to-hang-a-wall-of-handmade-ceramic-bowls-084738

How do you know what dimension of plate hanger to buy? The website doesn't explain this...

Choose the hanger by the diameter and weight of the plate. Make sure to follow the directions. The adhesive has to dry overnight. Good-luck!

3M offers an array of hanging "tools" that I have used for my plate wall. They are adhesive and velcro, and hang up to 25 lbs. each.

There are ledges just for this at Pottery Barn and Crate and Barrel that will do the trick and look a little less granny.

i used plain floral wire and a martha stewart tutorial. was super-cheap and easy (and i am not a crafty person). http://www.marthastewart.com/good-things/wire-plate-hangers

if the plates are at all valuable, either financially or sentimentallly, don't use the wire hangers as they chip the edges, are prone to suddenly giving way and you can easily end up smashing the plate when you take the holder off. You can get adhesive discs for this purpose which come with little loops for hanging which are much better. They vary in size - the larger/heavier your plate the bigger the hanger you need.

I found some at my local Hobby Lobby. They came with the hanging hardware. I've used the same ones in two different houses over the last 4-5 years and, so far, they've been just fine. We had an earthquake a couple of months back that really shook our house and while the plates vibrated on the wall, they hangers held just fine. They are like this one:http://www.google.com/products/catalog?client=safari&rls=en&q=plate+hangers&oe=UTF-8&um=1&ie=UTF-8&cid=12843983626217645579&sa=X&ei=s56QTfWLKo_AgQeP3uWtDQ&ved=0CFEQ8wIwAg#ps-sellers

I agree, i have a 35 plate collection on my dinning room wall. All my plate jangers have come from Hobby Lobby, i buy them in bulk. They are the cheap wire ones, .99-3.99. They have little clear rubber guards on the prongs so they do not scratch or chip your plates. The nail or screw that you put in the wall is way more important than the hanger. I have had mine up on the wall for 5+ years and never had one fall or break. Even with drunken neighbors slaming into the wall at 2am.

I used these, very happy with the results:
http://www.containerstore.com/shop/collections/display/frames?productId=10010750

The worst plate hangers to use are the wire/spring ones - They tend to wear down the edges of the plates and can cause chipping.

I use these triangular plate hangers from Tripar - They're available at hobby stores and eBay.
http://www.tripar.com/product.php?id=657683HUPN

@AbigailC do you have a brand or name for the product you've described? I'd like to search for it. Thanks!

I'm starting a plate wall above my dining table and have just been using the cheap plate hangers at Walmart. :P I'm not too picky though.

allplatehangers.com offers the adhesive disks and every order has free shipping.

Someone commented above that 3M has a product or two for this as well. I found that as well, its a part of their Command line. WAAAAAAYYY cheaper than ANY of the plate hangers out there. Here they are--hopefully they stick as well as 3M says they will:: http://www.target.com/p/3M-Command-Damage-Free-Hanging-Large-Picture-Hanging-Strips-4-ct/-/A-13713732

At Eisley Fine Art, we do custom acrylic plate hangars that are extremely secure and reliable!

http://www.eisleyfineart.com/presentation--display.html