I found the book Selling the Invisible by Harry Beckwith to be a very interesting and inspiring read. Those of us working in software development deal with the invisible all the time. While some of us may write shrink-wrap software, and can point to the box as proof that our product exists, even that product can be mostly invisible: anti-virus software, for example, should be invisible until it tells you it found and eliminated a virus (and maybe even then).
Selling the Invisible is about marketing and a lot more: some of the best marketing comes from having a good product or service, and happy clients or buyers. It comes from maintaining good relationships. I recommend this book. It gave me an idea for my company that could be profitable, and I've only read the book once through so far.
"Management" is mostly invisible - the worse management is, the more visible it is. The best managers (I'm told) often seem like they are neither busy nor doing "any work," because they've done a lot of work to keep potential problems from turning into actual problems. Managers could do with reading this book, considering their bosses, peers, customers, suppliers, and direct reports as "customers", all of whom to maintain good relationships with.
Software development methods can be invisible too. Particularly agile methods that don't produce many artifacts other than the software itself. The recommended "big visible charts" (in particular the scrum burn-down chart adapted for XP) help make the invisible stuff visible, and help keep a good relationship with the customer.
In fact, I thought Kent Beck wrote a message in the IXP mailing list that sounded like the "positioning statement" exercise of Selling the Invisible, but now I can't find it. I'll attempt to do the exercise here, using me as an XP coach/project leader. The positioning statement answers the questions of Who, what, for whom, what need, against whom, what's different, and what benefit.
Keith Ray is a coach and project leader for small to medium-sized projects (up to 10 programmers) which need to ship good quality software, quickly and/or frequently, whether the desired features are vaguely defined, changing, or very specific. Unlike many in this industry, Keith Ray has been developing software for over 15 years, and has participated in many successful projects in several product areas, creating and shipping good software at a predictable pace. Keith Ray uses good, context-specific, practices to enable you to get the important features you want as soon as possible.
You notice I don't say "XP" or "agile" in this statement - people are looking for solutions to their problems, and don't care about the techniques I use (I hope). What's your positioning statement?