One of the things that surprises some recent graduates is how "worthless" your school time is. Nothing you do at work resembles what you studied at school, at least on first blush. What your schooling is supposed to do is give you a good feel for the operating principals behind what you do. Even though you don't learn about pumps or piping (or at least very little), you do learn about turbulence and friction losses.
When you're an engineer, you do most of your work with very basic tools. Books like Crane TP#410 are all you need for the majority of your work. Occasionally, you will get into more complex problems when you run into either indeterminate problems or cases that would just take too long to do by hand. In those instances, we resort to computer modeling programs. Even then, though, we back up those calcs with hand calcs when it really counts. For critical structures, like say the hull of a TLP, all computer calculations are backed up by hand, no matter how intensive.
Here are a couple of examples that I've played around with:
Pipe-Flo allows you to create hydraulic models of facilities and test them with whatever flowrate you want. Very useful for pump selection and control valve programming. Pump selection is always tricky by hand because centrifugal pumps' flowrate depends on the friction loss in the pipe. The friction loss is defendant on the flowrate, so pump selection is an iterative process.
Caesar II is a pipe stress analysis program I just learned how to use. It tells you where to anchor your pipe, including loads from thermal expansion.
Hysys is used by process engineers (sort of a hybrid between mechanical and chemical engineering) to design plants. I haven't messed with it too much, yet, but I hope to learn it soon.
Finite Element Analysis is used to figure out how complex structures will react to stress. One program that's very good that I know is Solidworks/COSMOS.
And then of course, there's AutoDesk. The granddaddy of all AutoCad programs. So many expansions are available, so you can get it to do whatever you want. It's also the industry standard.