A good resource for researching treasury bonds is http://etfdb.com/etfdb-category/government-bonds/ they have lots of information about different types of treasury bonds.
The symbol for iShares Core GNMA Bond ETF in NASDAQ is: GNMA.
The symbol for Vanguard Total International Bond ETF in NASDAQ is: BNDX.
The symbol for Vanguard Emerging Markets Government Bond ETF in NASDAQ is: VWOB.
The symbol for Vanguard Intermediate -Term Government Bond ETF in NASDAQ is: VGIT.
The symbol for Vanguard Short-Term Corporate Bond ETF in NASDAQ is: VCSH.
The symbol for Vanguard Long-Term Government Bond ETF in NASDAQ is: VGLT.
The symbol for Vanguard Intermediate-Term Corporate Bond ETF in NASDAQ is: VCIT.
The symbol for Vanguard Long-Term Corporate Bond ETF in NASDAQ is: VCLT.
As of July 2014, the market cap for iShares Core GNMA Bond ETF (GNMA) is $34,846,000.00.
As of July 2014, the market cap for Vanguard Total International Bond ETF (BNDX) is $1,480,633,000.00.
According to Bankrate, some of the main benefits of using bond ETF investments include the ability to sell them at any time as well as the option to invest in overseas currencies with some ETF's.
Here are some research tools: http://www.marketwatch.com/investing/research-tools . Scroll down to "ETF Center" and select the tool you're interested in.