Capers Jones has written an article introducing the concepts and methods of function point estimating. It's useful knowledge for project managemers, analysts, designers and tech team leads.
The article is particularly useful as it gives you a simple framework to try FP estimating yourself. It also points you at more sophisticated tools in case you want to explore further.
Mr Jones is an expert in the field and author of several books on IT estimating, quality and more. See what he has to say at Modern Analyst.