I think that many people can admit to fantasies of an early retirement. I know that I have had more than a few daydreams about the subject.
Over the years I have found a few really good resources (and many more really bad ones) to seek advice on early retirement. I think that the best resources are actual people who have retired early and are willing to share their thoughts.
I have found a few common themes among those who have retired early:
1) Living below your means (LBYM).
2) Maintaining a diversified investment portfolio on which to draw from.
3) Using a conservative 4% rule of thumb as a baseline for withdrawing from your retirement savings.
Since I am not retired (yet), I'll refer you to my sources for more information.
How to Retire Early and Live Well by Gillette Edmunds focuses on building a diversified portfolio on which to draw living expenses from.
Retire Early and Live the Life You Want Now by John F. Wasik is a very good all around reference on early retirement.
Cashing in on the American Dream by Paul Terhorst focuses on reducing expenses, and advocates selling your house, and moving to a less expensive residence, to finance an early retirement. Unfortunately this book is out of print, but might be available at some libraries.
The Retire Early Homepage is maintained by John P. Greaney, an engineer who retired at age 38. This site gives a lot of general information about early retirement. He strongly cautions against retiring too early when your savings aren't really enough to sustain you for the rest of your life. I think that some of his older material is of more practical use than the more recent entries.
Early Retirement Forum is a message board for those who have retired early, and those who intend to. There are various forum topics broken out by the stages of planning for an early retirement.
Retire Early Lifestyle is an inspirational website by a couple who retired in their 30s. They spend a lot of time traveling the world, and are able to keep their expenses amazingly low. They also have an e-book available on CD-ROM which I recently purchased.
One last note, on the Internet, you may come across the acronym FIRE which stands for Financial Independence Retire Early.
More Links for Early Retirement
Early Retirement Housing