Moody's thinks the U.S. won't default on its debt and will keep its Aaa rating, but could get a negative outlook (AP at Yahoo Finance):
"The credit rating agency said it thinks that even if the nation's $14.3 trillion borrowing limit isn't raised by Tuesday's deadline, the government would give priority to making interest payments on its debt and thereby avoid a default."
iShares Barclays TIPS Bond Fund (stockcharts.com)
iShares Barclays 7-10 Year Treasury Bond Fund (stockcharts.com)
iShares Barclays 20+ Treasury Bond Fund (stockcharts.com)