If you use Dojo, have a look at the fabulous widgets called TurboWidgets from TurboAjax.com: it's available for non-commercial and commercial usage. One of the great widgets is a data grid which can be customized in a wide variety.

As I've discovered in the TurboWidget forums, they're working on a virtual data grid. Imagine you want to display a list of 100,000 or more items which can be a major pita especially when working with slow internet connectivity. The solution is a real virtual data grid

He points to a demo they've posted and includes two screenshots, one of the previous situation with data grids like this, and a shot of theirs in action (loaded with 100,000 rows).