I don't think the data are accessible as a CSV file, but try FINRA's Advanced Screener. It allows you to search for government, corporate, or municipal bonds using a wide range of criteria. FINRA also publishes TRACE Market Aggregate Information, which lists the most active investment grade debt securities and information about them.
For general information on both domestic and international debt markets, the Bank for International Settlements is a good place to start. They offer data in CSV format, although it isn't as specific as the data from FINRA's screener.
I found a site that lists 101 Free Resources for Bond Investors; one section is devoted solely to bond market data. They list data sources like the FINRA data I linked to before, as well as sources specific to certain types of bonds, e.g. municipal bonds, Treasuries, corporate bonds, etc.