James Marshall
Deputy Director, Federal Benefits Institute
National Active & Retired Federal Employees Association

I’ll reemphasize the importance of first sending folks to the actual host government source web sites (i.e. OPM, Social Security, TSP, Medicare, etc.), especially in regards to making sure folks use the most up-to-date forms and processes.  But other web sites (such as can be useful when trying to help someone understand “government speak”, expanding on a topic that the government web site doesn’t explain very well, or helping someone locate a difficult-to-find answer to their question.
When I speak with the Federal population, I teach them that when they are searching for information about their Federal benefits online, it can often be easier to find what they’re looking for using a major search engine like Google or Yahoo instead of the less sophisticated search engine provided by the actual government web site.  As long as they use key words, (i.e. OPM, CSRS Offset, spousal survivor benefit, etc.), a search engine like Google will usually yield the exact location of the government web page that they need much quicker than trying to find the same page using the government web site.  It’s also important to emphasize that if they use a major search engine like Google that they first attempt to obtain the information they need from the government web pages yielded from the search before they start looking at the search engine results from other random non-government sources.
If the non-government source helps to make sense of the government information, that’s good… but they should be cautious, especially if the non-government source seems to contradict the government information, then the individual should either communicate with the government source directly for explanation, OR contact NARFE.  As you know, there are many entities online that claim to be “subject matter experts” in the areas of Federal benefits, but they often know very little OR just enough to make them dangerous to the Federal population, and unfortunately their web sites will often come up in search engine results.
Here are some additional URL addresses that you might consider, in no particular order:

FSAFEDS for Flexible Spending Accounts (healthcare, dependent care, & limited expense healthcare)
BENEFEDS for the Federal Employees Dental & Vision Insurance Program (FEDVIP)
Consumers' Checkbook Guide to Federal Health Insurance Plans
NARFE Federal Benefits Institute (archived and upcoming webinars are also on this web page)
OPM Publications and Forms
Directory of Headquarters Level Agency Benefits Officers (Federal employees often don’t know who their agency benefits/retirement officers are.  This web page includes a directory of folks who can assist them with identifying who they should contact for assistance with Federal benefits & retirement while still employed).
Info from AARP Regarding Second Careers
FEHB and Medicare Booklet
FEHB and Medicare Fast Facts
Medicare and YOU web site
Other Insurance Assistance Programs
National Council on Aging
TSP Forms and Publications
TSP FAQs  A web site from the U.S. Securities and Exchange Commission to help folks learn more about managing investments and hiring a professional financial advisor, if desired.