Search Bloomberg (available in the Business Library) to get a credit rating of a government/corporate bond by Moody's, S&P and Bloomberg composite. Type the [ticker symbol] CORP RATE and hit < GO >. Example: IBM 4.125 05 CORP RATE. RATD will show Rating Agencies Definitions.
Use Mergent Online. Search for a company and go to the Long Term Debt section. Select a bond.
Use Capital IQ (available in the Business Library). Search for a company. Under the "Fixed Income" heading choose Credit Ratings.