The Federal Election Campaign Act (FECA) limits the amount of money individuals and political organizations can give to a candidate running for federal office. You can donate to more than one candidate in each federal election. The current contribution limits are $3300 to each candidate during the primaries and $3300 to each candidate during the general election. (Source: Federal Campaign Finance Laws)
Federal Election Commission
Maintained by Center for Responsive Politics
This website from the Federal Elections Commission contains a database of campaign finance reports.
Followthemoney.org Provides free access to federal and state level campaign contributions.
This website from the Federal Election Commission outlines how to register as a candidate.
This web page provides an explanation of what a PAC is and what roles it plays in political campaigns.
“Dark money” refers to spending meant to influence political outcomes where the source of the money is not disclosed. Here’s how dark money makes its way into elections:
Source: opensecrets.org