Two interesting articles describe how interactive visualization tools can be used for deriving insight from large business datasets. They both describe tools developed by the Human-Computer Interaction Lab at the University of Maryland. For James Bond fans, this place reminds me of Q branch -- they come up with amazingly cool visualization tools that save your day.
The first article "Describing Business Intelligence Using Treemap Visualizations" by Ben Shneiderman describes Treemap, a tool for visualizing hierarchical data. Know smartmoney.com's "Map of the Market"? Guess where that came from!
The second article "The Surest Path to Visual Discovery" by Stephen Few describes Timesearcher, an interactive visualization tool for time series data, such as stocks. For full disclosure, I've been involved in the development of the current version in adapting it to eCommerce-type data and in particular auction data such as those from eBay. Timesearcher2 is capable of displaying tightly-coupled times series and cross-sectional data (ever seen anything like it?) That means that each auction consists of a time-series describing the bid history but also cross-sectional data such as the seller id and rating, item category, etc. For more details on the auction implementation check out our paper Exploring Auction Databases Through Interactive Visualization.