I don't know how common this is, but with a dual-monitor setup I tend to have one in landscape and one in portrait. The portrait monitor is good for things like documents, or other "long" windows like log files and barfy terminal output. The landscape monitor is good for everything that's designed to operate in that aspect ratio (like web stuff).

More generally, there's usually something I'm reading and something I'm working on, and I'll read from one monitor, while working on whatever is in the other.

At work I make use of four Gnome workspaces: one which has distracting things like email and project management gubbins; one active work-dev workspace; one self-development-dev workspace; and one where I stick all the applications and terminals that I don't actively need to look at, but won't run minimised/headlessly for one reason or another.