Im planning on building an office desk,a few questions...?

Question

what is the name of those wheel-and-rail things that hold drawers up and allow them to slide freely? and What kind of inexpensive wood would be good for a strong desk?

Answer 1

You are looking for "drawer glides." They come in different weights. If these are drawers that will hold files, be sure to buy some that are rated strong enough for files.
If you want something fast and cheap, you can buy a door and put it on trestles or ready made file drawers.
If you want something to look good and last, I would suggest maple plywood for the flat surfaces and drawer fronts. It's a tight grain pattern and is easy to work. It has a contemporary look with a clear finish or light stain. It can look traditional with a cherry or deeper stain.
Plywood will be heavy and strong and won't need a lot of reinforcement. If this is to be a desk on which you will be writing or drawing, avoid a plywood that has a strong grain pattern like red oak or ash. (In time, the soft tissue in the grain will wear at a different rate that the harder tissue and you will have an uneven surface.) With any plywood, you will need wood edging to finish the raw edges. Pending the style desk you want, it could be a simple flat edge, or if you want a traditional look, you can get edging with an ogee ("S" shape,) detail.
If you will draw out your design beforehand, some yards will make the large cuts for you for a small charge. If you are going to make the cuts yourself, be sure your saw blades are very sharp, then you will have fewer problems with splintering. If you don't have a design or pattern already, home centers such as Lowe's or Home Depot will have do-it-yourself books of designs, or you can look at the library or a good book store.

Answer 2

Uh, if you have these components and need to ask this question, I see many issues down the road. You will be better off to go to a manufacturer's website and select what you desire. If the compents aren't compatible you will not be able to select them.