If you've been kicking yourself for missing out on the historically low mortgage rates back in June, let's just hope you've been wearing soft-heeled shoes. True, the refinancing window came and went faster than you could ask, "Is there a draft in here?" -- but, hey, borrowing costs are falling again.

Bankrate is reporting that mortgage rates have fallen for four weeks in a row. The average 30-year fixed-rate loan is being doled out at 5.79%, while the more attractive 15-year option is down to 5.11%. No, we're not at record lows again, but we're close. Borrowing costs haven't been this low since July.

Stockwise, that's good news for homebuilders like Lennar (NYSE:LEN), D.R. Horton (NYSE:DHI) and KB Home (NYSE:KBH) who will now be able to take advantage of enhanced elasticity in the homebuyer budget. Lenders like Countrywide (NYSE:CFC) clearly stand to benefit. Even unlikely H&R Block (NYSE:HRB), which is knee-deep in the mortgage business, will also reap the benefits of cheaper financing.

But what about you? Are you ready to refinance your home or dust off those shelved plans to find a new homestead? If so, you've already learned that this finicky window of opportunity doesn't stay open forever. The low rates might also give you the flexibility to go with a simple fixed-rate loan.

Right now a quarter of all new home loans are being written up as adjustable-rate loans. Sure, they start off attractive, but with rates more likely to head higher than lower, that could prove a costly decision down the road.

So think smart, but, if at all possible, think fast.

Yes, our Home Center is a great place to start gathering research on the home hunting process, but how long do you think these low rates will last? If you're selling your home, do you really need a realtor? What is the best way to negotiate a house deal? All this and more -- in the Buying or Selling a Home discussion board. Only on Fool.com.