The symfony 1.x branch of the framework started in 2005 and the latest stable version and long term support release is symfony 1.4. As of November 2012, symfony 1.x is not maintained anymore and you are encouraged to have a look at newer Symfony versions for any new projects.
Learn symfony: 24 tutorials of 1 hour each, that's all it takes to build up a complete and effective application from scratch. Definitely the best way to become a good symfony developer!
ReadThe reference guide: The Symfony Reference Guide is a book where you can easily find answers to your questions at your fingertips. This is a book you will keep with you whenever you develop with symfony.
ReadDo more with symfony: This book is the symfony 2009 advent calendar, a set of 24 tutorials about advanced symfony topics, published day-by-day between December 1st and Christmas 2009. All tutorials are available in five languages: English, French, Spanish, Italian, and Japanese.
Read