o Credit Rating Companies

The three main debt rating firms are:
1) Standard & Poor’s
2) Moody’s Investors Service
3) Fitch Ratings.
The companies measure the likelihood that the issuer of a bond will fulfill its payment obligations in a timely manner, with respect to both interest and principal commitments. A rating of "AAA" means the firm's credit is good and the default risk is almost zero, while a B rated bonds are risky and considered junk or non-investment grade bonds.

You can find bond ratings on the FINRA website.

• FINRA
• http://cxa.marketwatch.com/finra/BondCenter/Default.aspx
  

Allow me to review the top of the register of companies whose corporate bonds were not so long ago rated "investment grade" by the rating agencies:
1) Lehman Brothers
2) Bear Stearns
3) Countrywide Financial
4) AIG
5) IndyMac Bank
6) Washington Mutual

...and others too numerous to list.

Who is rating the rating companies' performance?

I've created my own rating system for the rating companies. An "A" means "good job pal, you are able to properly assess the risk of a corporate bond". An "F" means "you suck ass, you might as well have chosen that bond rating randomly." S & P's, Moody's and Fitch's ability to rate companies - not so good. I rate them all a suck ass "F".