Ruby on Rails is an Open-Source framework for the rapid development of Agile Database-backed Web Sites.
It is the brainchiold of a single individual called David Heinemeier Hansson.
Although Ruby is easy to read, it has a steep learning-curve for novices. It is currently attracting a good deal of attention, but it is actually deployed on a very small scale compared to established approaches like PHP/MySQL.
I'd like to recommend a book but there are three or four due to be published soon !
Just go to Amazon and search for 'Ruby on Rails'.