One of the great things about shopping for a computer desk is that you can go with any type of desk that you like even if it's for a small space. There are no longer any rules, regarding computer desks. If you have a really small space, you can use a dining room table, or coffee table, for your computer. If you have a laptop, you don't even need to buy a specific desk! But if you want something computer specific, there are a number of companies that you should check, when shopping.
Ikea is the best go-to store when you need something to fit into a specific space. They make all sized desks, but specialize in small spaces. Whether you want something to be flush against a wall, or to fit into a corner, Ikea has it for you. And, with easy shipping and inexpensive prices, is the first place to look online. Even better if you have one within driving distance, so you can see all the options, they have an entire floor dedicated to home office furniture. And be sure to look at their dining room table options, as well as their credenzas, because these also make for great small desks.
Overstock.com is another place to shop, they have pages upon pages of small computer desks, and their prices truly can't be beat. They have all styles, too, from high end to high tech. And, with free shipping, it's a great place to look. Another online source to check is Amazon.com, as they have a fairly large selection. Even if you don't plan to buy from these sites, it's worth the 30 minutes you spend browsing, so you can narrow down what appeals to you, and what you seek.
Go to your local close-out office furniture store, and see what fits your measurements, often you'll find great deals at these stores, and they're usually current. Consignment stores and flea markets are also a place to look for a small desk. Remember it doesn't have to be computer specific! Also, if you have a Pottery Barn or Crate and Barrel in your city, look there. Sometimes it helps to see these desks in person.