The best BI visualizations bring out essential information that might otherwise remain hidden in data. A Washington Post visualization of President Obama's proposed $3.8 trillion budget for fiscal year 2011 does just that. The Post's viz tells a complete story: Budgets include both expenditures and revenues and this viz counter-balances the two. Contrast with other budget views, such as one that appeared in the February 1 New York Times, that focus solely on spending, telling only half the story but with a much deeper level of detail. There's much to be learned from the Times example as well, in particular about visualizing change.
Strong visualizations speak for themselves; if a picture is truly worth a thousand words, we shouldn't need a lot of text to explain it. I see a need to expend very few words to describe what I like about the Post's budget viz. It makes two key points crystal clear: the magnitude of borrowing necessary to complement receipts on the "Where the money comes from" side and the huge amount of mandatory (versus discretionary) spending on the "Where the money goes" side. Each side broken down by major components, and if you'd like to explore them further, you can via tabs for historical taxes/revenue, spending by type, spending by agency, and surplus/deficit. Those charts make effective use of interactive effects -- mouse-over data labeling and normalized and drill-down area charts -- without presenting so much data that the viewer is overwhelmed, losing track of the context.