This is an excellent gateway for you to select reliable sources. The PSA is the professional association that represents academics in politics in the UK and this page has been made as gateway to a huge variety of sources in all different areas in politics. Search by country or by topic.
Here is an excellent source made by law professionals, but obviously with interest for politics students.
It leads you to both newspapers (national, UK, and regional), as well as legislation (UK and EU).
CountryData enables countries to share official national development data with the global user community. National and international data users can now easily access statistics used to track development progress at the country level.
The Hansard Society is an organisation that studies and promotes political engagement in democracy. They are supported by Parliament, but are are an independent organization. They produce very valuable reports, which you can access (almost all for free) from their website.
Election Guide is provided by IFES, an international nonprofit dedicated to the building of democratic societies. Launched in 1998 through a generous grant from USAID, ElectionGuide is the most comprehensive and timely source of verified election information and results available online. Its content is also available on CNN Election Watch.
This site provides very comprehensive and reliable information about electoral results all over the world, as well as explanations of electoral systems/processes. For data on Voter Turnout, for instance, go to the bottom of the Home page and you will see a direct link to their DataBase.
This is a data bank that includes information about elections all around the world. It does not go very far back in the past and it does not provide contextual information for most of the cases, but it does provide a guide on what is happening in today's world in terms of elections and their results.
Direct link to the Eurobarometer - surveys carried out regularly in all member states of the EU since at least 1970s. Includes questions on satisfaction towards democracy and attachment values towards EU, as well as topical issues. Also available on paper in the library.
Human Rights Watch is an independent, nongovernmental organization, supported by contributions from private individuals and foundations worldwide. It accepts no government funds, directly or indirectly.
An international media development charity, IWPR is led by senior journalists and peace researchers, with staff drawn from established media such as the BBC, The Guardian and Reuters. The Institute is registered as a charity in the United Kingdom, an organisation with tax-exempt status under Section 501(c)(3) in the United States, and a Section 21 not-for-profit organisation in South Africa.
This takes you directly to the Research and Publications page, where you can access a very wide range of data from their opinion polls. Go in particular to their Research Archive and filter by Theme (political?) and Year.