I started to develop automated regression tests for biggest Netherland's auctionmarktplaats.nl (owned by Ebay) in 2007 year. We used Mercury QTP that time, but later we have moved to an excellent Open-source project Selenium RC, Java and Eclipse IDE. It was full time job and I participated in test-framework development and implemented some tests as well. Team had 7 members. Rest of projects were developed just by me alone, on freelance. Selenium RC can be used for data-mining as well and some projects were completed for this purpose.
Used technologies: C#, XPath/HTML/CSS-selectors, Selenium RC, Selenium WebDriver.