The Veterans Administration site which has all the information on VA Mortgage, VA streamline refinance, Veterans Benefits, IRRRL loans, and VA documents.
HUD site with lots of good information on FHA and HUD guidelines. If you have a FHA mortgage, Streamline FHA loan, FHA Purchase, 203k FHA loan,or FHA construction loan, this is the site to find out all of the FHA as well as RESPA knowledge.
Mortgage-Calc.com provides you with mortgage calculators, financial calculators, amortization tables, car loan calculators, and free links!
The Mortgage Bankers Association of America maintains the best one-stop reference for real estate finance information and mortgage loan information.