Even though men's shoe sizes 14, 14.5 and 15 (US) are considered "large," they've become easier to find, thanks to the web. If you wear a U.S. size 16 or above, there are still some options, but naturally, the larger you go, the more limited the selection.
Whatever size you take, your best bests are the sites listed below. In addition to the links, I've provided a bit of information on each of the retailers.
In addition to having large selection from top brands and designers, Zappos offers some of the best looking shoes for guys who wear larger sizes. Of course, the larger you need, the less selection there is, but they even offer a good selection of US size 20 athletic shoes. (Buy Direct)
Ever wonder where the large-footed basketball players of the NBA shop? Well, wonder no more.
With a huge selection of shoes in US sizes 7-22, Friedman's has fit athletes like Magic Johnson, Shaquille O'Neal, Hakeem Olajuwon and Scottie Pippin -- but they don't just carry athletic shoes. In fact, it's likely their selection of sandals, dress shoes and casual shoes that has large-sized celebrities coming back for more.
If you can't make it to their reknowned store in downtown Atlanta, don't worry, you can now shop online or via their mail-order catalog. (Vendor's Site)
With dress, casual and athletic footwear from major brands, this is definitely the first site I'd check if I wore a size 20 (US). Like all the others, they offer more styles in smaller sizes. (Buy Direct)
One of my favorite things about this site is that they make it easy to find your size by putting the US size and width (as well as the Euro size) in the same pop-up menu. For example, if you need a size 15 wide, you select it in one place, and all options in that size are returned. (Buy Direct)
Though I've never shopped with them myself, Oddball.com has been around for a long time, and I've had several readers write in to recommend them for this list. They carry men's brand name shoes in sizes 13-20, and have a good selection of dress, athletic and casual shoes from names like Adidas, Skechers and Steve Madden. (Vendor's Site)
Here you can search by US or Euro sizes, and find a good selection of shoes in US sizes 20 and below. As an added bonus, if you need a wider or slimmer than average shoe, this site should have you covered. (Vendor's Site)
This site carries athletic, casual and dress shoes in sizes up to a US 20, but they also have these larger sizes in wider than average widths, making them a must-see for guys who leave a large footprint. While the selection isn't huge, it's good, and the site is very easy to search. (Vendor's Site)