I'm playing around with the Rapidminer Finance and Economics extension, from Broad Reach Analytics, and I like it. It's a slick and fast way to get financial data into your processes and there are lots of operators that let you get data from Bloomberg, the World Bank, and Yahoo.
It would normally take me 30 minutes to an hour to cobble together stock quote data from Yahoo into a spreadsheet, then validate the dates, and import them into Rapidminer. Now, using the extension's operator, it took me 5 minutes.
Just for fun, I created this advanced S&P500 chart using color coded VIX values, which took another 5 minutes. Done!
This extension holds great promise but it appears there haven't been any recent updates. Still, one extension to keep an eye on.