What IT technologies are the most underused? Here are my suggestions, I am sure people here can add plenty more (or disagree with me).
There is already an active thread about desktop Linux, so I will not add more to that, except to say that I think Linux is an excellent choice for naive users who always manage to get Windows messed up or infected with malware.
The thing that started me off on this was Python. I have been coding a new site (my most ambitious in terms of my own code so far) in Python and it has been much nicer to work in than PHP - but the latter wins on popularity (look at how active the PHP forum here is). Why? It is also of broader use than PHP: PHP is pretty much just for the web (yes I know about it CAN be used elsewhere): Python is used for every thing from scientific number crunching (Numpy) to music players (Quod Libet rocks).
Next, some of the less well know webservers. I installed Cherokee for a test server because changing the config as I switch between different projects is easy. Its fast, memory efficient and easy to administer - but no one seems to use it. Sure, its not going to be the right choice for shared hosting, but it seems an excellent choice for a small site using a VPS.
Next disk encryption in general. Laptops are easy to steal. Why do so many people people fail to encrypt the hard drive? Its not that difficult these days.
I far prefer to write a document of any length in Lyx rather than a word processor: most of the power of Latex with a simple GUI reducing the learning curve. OK, its not as good for collaborative editing, but for documents of any length by a single author it is far more productive.
RSS readers: huge time savers, far easier than checking news sites in a web browser, but most people do not even know what they are.
I can also suggest some technologies that people need to use less (FTP, IE6....).
