Basically one can create a worksheet and set the publishing option to output RSS (or ATOM or any format of your choice) and select an appropriate publishing frequency. Once this is done whatever you add to your worksheet is available for anyone who subscribes. Also there is an option to customize and publish a select range of cells and not an entire sheet.
Now it is possible for Clickables (Google Gadget that I developed few months back) to use spreadsheets and provide persistence bookmarking of shared links. Also, integration with Yahoo Pipes! can bring about a lot of data mashup feeds.