At BillGuard we use Yodlee's API. Yodlee in turn have several ways of getting the data out of banks - with some they have APIs while with others they just scrape it.
Mint used to use Yodlee, but since they have been acquired it seems they've switched to using Intuit's internal solution.
In the very beginning, the founder scraped several sites without using an API.
Wesabe screen scraped as described in this post by the founder about how Wesabe lost to Mint. http://blog.precipice.org/why-wesabe-lost-to-mint Here is an interview with Aaron Patzer, founder of Mint, talks a bit about how they acquired data. Key point - some banks support a data exchange API called OFX. Yodlee aggregated that access and scraped those banks that didn't support OFX. http://www.sramanamitra.com/2009/07/05/the-web-startup-success-guide-part-2-case-study-of-mintcom/