If you really want to maximize efficiency, there are a few no-brainers.  Besides cordless keyboard and mouse, and double-monitors (the obvious choice being flat-screen monitors), the next improvement is to mount your monitors above the desk surface.

Flat-screen monitors come with industry-standard bracket mount holes on the back.  You simply find a mounting system suitable to your office/desk environment.  There are poles, swivels, telescopes, direct to wall, etc.  Google ‘flat screen monitor brackets’ and you will find an impressive variety spanning a range of prices.  Pick the one that matches your budget and workspace layout.

I purchased two mount brackets on EBay for $9.99 each–very simple, but all I needed.  What was for years a tight keyboard nearly in my lap is now a spacious work area. 

Two screens at perfect eye level, above the desk, and all for around $20.  Who wouldn’t make that investment?