Some time ago, I built a roll-top desk -- from a kit, of course -- and I really enjoyed the detail work of sanding and fitting all the pieces together to get the three boxes of wooden pieces assembled into a ten-drawer, 550 pound monster with all kinds of cubby holes and a couple secret spots. I wouldn't suggest you do that, unless you have a couple months of spare time. Instead, look below the fold for a sampling of desks for your home.
Wow; where to begin? The horizon of desks is nearly limitless, from small kitchen desks, to home office computer models, to monster, impressive desk/credenza styles. Take a look:
Computer desks -
- they're available in modern, glass-topped models, classic wooden versions, and ultra-chic styles. They will fit flush against a wall, or in a space-saving version that will neatly occupy a corner; ideal for a small bedroom office.
Also on the market are those desks that stack your computer gear, vertically, for saving space -- this, I suppose, if you're stuck with only a closet for a space. I've seen a couple of those.

You can find desks that are an armoire style, or a hutch. I really like these kinds of desk if you don't want the appearance of an office, as the architecture will fit right in with your other furniture. The good thing about these versions is that they look quite nice with the doors open or shut so you don't have to concern yourself with having to keep the unit closed all the time.
Single or double pedestal desks are widely available and are most useful if you have a minimum of paperwork and stuff to keep handy.

I also like the credenza style of desk; I'm into the orientation of this desk; if you have a "blank" wall to fill, this is surely the model for you.

The simplest version, of course, is just a "plain jane" writing desk. Don't be confused by the simplicity of this design; there are some really well-crafted versions of this tried and true model. A great point about this kind of desk is that it doesn't tend to build up a lot of junk on it, given the limited storage space. Sweet.