Though some people don’t like the UML, its value as a modeling notation cannot be overlooked. Although I’m not a strict UML purist, neither believing in UmlAsBlueprint or UmlAsProgrammingLanguage instead opting for UmlAsSketch.

Here are some great (free) resources for getting up to speed on the UML:

Online study aids:

• Scott Ambler's guide: http://www.agilemodeling.com/essays/umlDiagrams.htm
  Scott’s guide is really great, and he in fact covers a TON of diagram types (including ERDs, Data Flow Diagrams, etc.)
• Borland's UML 2 study guide: http://bdn.borland.com/article/0,1410,31863,00.html
• Sparx System UML tutorial: http://sparxsystems.com.au/resources/tutorial/index.html
• Embarcadero's UML site: http://www.embarcadero.com/support/uml_central.html
• Martin Fowler’s UML bliki: http://www.martinfowler.com/bliki/uml.html
• Conrad Bock’s UML 2 articles: http://www.conradbock.org/bockonline.html#UML2.0

Resources:

• Visio shapes and templates for UML 2.0: http://www.phruby.com/stencildownload.html
• Download the complete UML 2.0 spec (boring, but maybe helpful):  http://www.uml.org/

Books

The best, UML-only book for sure is Martin Fowler’s UML Distilled, 3^rd ed. Subtitled “A Brief Guide to the Standard Object Modeling Language,” it weighs in at a mere 192 pages (including index, bibliography, blah blah blah).

If you really want to understand the value of UML in context (as well as development process, object-oriented analysis and design, and more), I must recommend Craig Larman’s Applying UML and Patterns, 3^rd ed. See what I wrote about it here and see why David Hayden calls it the best development book he bought in 2004, period.

Ezequiel Cuellar's Notes on Applying UML and Patterns were very helpful for a review:

• Section 1 - Development Process
• Section 2 - Requirements Modeling
• Section 3 - Architecture
• Section 4 - Static Modeling
• Section 5 - Dynamic Modeling
• Section 6 - Design and Implementation Techniques

Also check out David Hayden’s blog post series.

Certifications

What would a modeling language be without certifications? There are two vendors offering UML certs. The OMG, the group that develops the UML, has their cert which you can learn about at http://www.omg.org/uml-certification/index.htm.

IBM also has a single test dedicated to it, Test 486: Object-Oriented Analysis and Design with UML http://www-03.ibm.com/certify/tests/edu486.shtml.

In passing the IBM 486 exam, I studied the two books UML Distilled (Fowler) and Applying UML and Patterns (Larman). Your mileage may vary.