UML is a notation, not a joke. Notation is a form of communication and communicating in a standard way is a good thing right?

For those really interested in learning UML the 'official' books are:

The Unified Modeling Language User Guide
The Unified Modeling Language Reference Manual
The Unified Software Development Process

Note that the third book puts a process around using UML, but in itself it is not a process. People commonly mistake UML for something it isn't, often confusing themselves with the reams of paperwork often associated with various software processes that use UML as the notation component.

UML is a very extensive modelling language and with so many diagrams and ways to express yourself in it, it's easy to understand folks confusion and feeling that it's exhaustive. It's important to note though, the UML designers encourage you to pick and choose which parts you use rather than feel UML is all about specififying everything to the nth detail using each diagram type. The purpose of the notation was not to force that. Adopting the right process for you is important.

Personally I use two or three types of diagram and easily got into the habit of drawing them and using them in communicating plans to others. It's very easy to teach people what you mean by them in a few minutes and I found it a great way of establishing a notation amongst a team - very useful for brainstorming quite detailed development plans.

I also used Rational Rose for my modelling. Rational Software have their own processes that Rose works amongst and I can't suggest getting into those, but I can say Rose was a decent UML editor (and a lot more, more than you would need in many cases). Since then I've found plenty of cheaper and open source editors that do the job well (the names don't spring to mind, it's been a while now).

For those interested, the shortform version of all the above books UML Distilled: A Brief Guide to the Standard Object Modeling Language can usually be found pretty cheaply and gets through the diagrams in a very quick and understandable manner. If that whets your appetite the user guide is a pretty detailed follow up.

I also find this UML tool to be useful... works online with flash, never have to download anything and it saves your graphs locally on your computer...

Gmodeler

Its very good... just click that link and then click launch.