Bond or stock dividends are interesting because they are market discontinuities. Unlike surprising earnings reports, revised analyst ratings, or lawsuits dividends are usually predictable in both amount and timing. You can capture a dividend by just buying and holding onto a investment that offers them, but then you are exposed to the price movements of that instrument.
For iShare and SPDR ETFs you can use this page to obtain dividend history data and charts. DividendInvestor provides a nice dividend report on their free website. It includes yields and timely updates on dividends. If you click on the “Dividends Paid Since” button you will get multiple years of dividend history.