Many Eyes is an excellent site for generating high-quality interactive visualizations of tabular data.
They just rolled out a key new feature – the ability to edit data after it has been uploaded to the system. Swivel implemented a similar feature a couple of months ago. The Many Eyes implementation is a bit more substantial than Swivel’s – Swivel lets you add, edit or delete existing rows, while Many Eyes permits the creation of additional rows, with some calculation features thrown in.
More importantly, Many Eyes keeps an annotated version history of the changes, and you can inspect previous versions. Unfortunately, only the latest version is “live” – you can’t apply visualizations to old versions. Swivel is similarly limited – with no history, you can’t compare visualizations generated from old and new versions of a given data set.
Both the Swivel and Many Eyes implementations of the editing function are quite awkward from a usability standpoint. I expect that these will improve in the future.