Yahoo Finance data from YQL is great. No, really.
Yahoo is where startups go to die, which is perhaps why I have an issue taking their offerings seriously. However, the Yahoo Query Language API is definitely something to look at. Publicly available API's, along with the ability to crowd-source (or just hooking in your own) API's is a potential power tool.
For a recent project, we took a look at what was available in YQL for financial data. It turns out Yahoo Finance data is available!
Here's a quick code snippet to get down and dirty with pulling currency conversions: https://gist.github.com/265014comments powered by Disqus