I recently wrote an article for on Flex and DataGrids Here is the intro . . .
Flex 3.0 offers a strong foundation of user interface (UI) controls by which users can harness a great deal of power to create beautiful UIs without having to toil in the details of low level functionality. Of these controls, the DataGrid sets itself apart by offering characteristics similar to a list or tree control (which are also listBase controls), but going further to offer an easy way of displaying columnar data without a complicated interface. In this article, I focus on creating a basic DataGrid and populating it with XML data by using only MXML tags.
Read the complete article at: Flex and DataGrids