I ordered a new computer last week and figured I should build a new desk to put it under. I don't have a lot of time available to invest in building one so this is what I'm thinking of. You can just barely see at the right end, the end of a longitudinal rail to prevent the top from sagging. It won't have to support a lot of weight, though, so I'm not too worried about sag.

No drawers intentionally. The desk I have now has a drawer that I don't really use. It's just a junk collector and I don't need that. Maybe I'll find some plastic trays to slide into the side openings. Keyboard and mouse (wireless) will slip into the middle section when I'm not using them.