Just adding to my previous argument to move away from massive spreadsheets (See WebApp vs. Data Tennis) is the infoSoft Global application FusionCharts. I'm a huge proponent of being able to visualize data in a way that will make the most impact for your audience. This shouldn't be sacrificed just because the application is on the web. As a matter of fact, it should be even more impacting with the speed of which information can be transfered and displayed.
We recently came across FusionCharts searching for a simple way to integrate web graphing with our already matured LAMP Application. The flash based graphing works well with PHP, Python, Ruby on Rails just to name a few. The best part is that all you need to do is feed it the right XML datafile and the graph is done. This makes it easy to read directly from a database (which we did) utilizing a few string manipulation techniques.
Did I mention that they have a free version?