So far this is the best online spreadsheet I've found. iRows has some critical features, like importing Excel files, CSV files, collaborative edits, and decent graphing capabilities. The site seems to work fine under Firefox 1.5 and IE 6, but Safari (as usual) had a few issues. One other neat trick: you can post your data on your own site, but make changes within iRows, and naturally it update wherever you've posted the data. These sorts of collaborative tools are exactly why web apps make a lot of sense in many situations. I can't wait to see more of these roll out of the Web 2.0 garage.