Google Spreadsheets, the most mature application from Google's online office suite, has suddenly become much better.
Now you can get email notifications when your collaborators make changes or edit some specific cells. You can also get notifications when someone submits new data using a form.
Google Spreadsheets autocompletes the value from a cell so it's much easier to enter repetitive data in a column.
If the existing features aren't enough for you, there's a new directory of gadgets that can be added to a spreadsheets and use existing data. You may remember the data visualization gadgets I found last month: they're part of this directory, which includes many other interesting gadgets. You can add interactive time series charts, Gantt charts, funnel charts, timelines, tables with filters and grouping, pivot tables, maps, search results and you can also create your own gadget that adds other missing features. As with any beginning, not all the gadgets work very well and the pivot table gadget created by Panorama doesn't seem to work at all.
To add a gadget, click on the "Insert" dropdown and select "Gadget". Each gadget can be embedded into web pages or added to iGoogle, which is extremely cool because the data is updated automatically.
Google Docs help center mentions a new visualization API connected with the new gadgets, but the documentation is not yet available. "The Gadgets-in-Docs for spreadsheets API should be used when you want to create user-facing features which are accessible from within the spreadsheet editor of Google Docs itself. This approach combines the Google Gadgets API with the Google Visualization API, to allow the developer to access data on the spreadsheet for use or presentation in practically any form they choose. Developers using this method should already be familiar with the development of Google Gadgets, and then only need to learn some basic additions provided by the Visualization API. Note that this approach currently only supports one-way interaction with the underlying spreadsheet (reading data), however, it has the advantage of enabling the publishing of gadgets created in a spreadsheet to other gadget-enabled sites, such as iGoogle."
If you find some interesting uses for the new gadgets, publish your spreadsheet and post a link in the comments.
Update:
A cool visualization gadget based on GapMinder World (you'll find in Google Docs as "motion chart")