In addition to library databases, there is an increasing availability of open data online. Open data is any data that is made freely available for others to download and reuse. Many open data repositories are highlighted here. To find open data, first consider who collects it. Which agencies and organizations have an interest in collecting data on your topic? Statistics Canada is a good source for Canadian data, while for international data, you might check the U.N. The World Bank is a good source for development-related data because development is its mission. If you find data on Google, consider whether the organization that collected it is trustworthy and whether it has partisan bias.
Data is also available from repositories hosted by universities or consortia. Some, like the International Consortium for Political and Social Research, are focused by discipline, while others are more general. Many universities have open data repositories where data gathered by their faculty is published.
When downloading data, there is usually an option to download the documentation. Make sure you download the documentation, as this will help you interpret and make sense of the data.