We're big fans of the one you're reading. But if you're looking for more opinions, check out the following:
Unsurprisingly, AARP.org has built a vast library of retirement resources, calculators, articles and even video on topics ranging from Social Security distributions to long-term care insurance.
The U.S. government published the retirement section of MyMoney.gov via the U.S. Financial Literacy and Education Commission. The site is largely a compendium of links to other government Web sites, which can be helpful if you want to apply for Social Security benefits or learn which laws protect your benefits in the event of a job loss.
You might want to look at your broker's site too. The Web sites of some mutual fund families like Fidelity, Vanguard and T.Rowe Price contain a wealth of free resources, tools, calculators and information.
For serious, long-term thinking from investment pros, check out the commentaries from leading bond investor Bill Gross at Janus Capital Group; Oaktree Capital Advisers co-chairman Howard Marks; and financial adviser Joshua Brown, who pens the blog The Reformed Broker.