For example, see this sample data at http://spreadsheets.google.com/pub?key=pnEs2B_37S-DGGFI6kdQZPQ. Using data from this spreadsheet, parsed as a JASON feed (see http://code.google.com/apis/gdata/json.html), the data is then loaded into a map by using a simple spreadsheet map wizard (See Here).

The data is read into the wizard, optionally, the map configuration can be altered, the map is viewed online, and then the code is optionally generated and returned to the user... I think even I can handle this one!

Once the map is created the code can be used to quickly embed the map on a website or upload to a Google pages account. Those of you with no google account need not worry as a nifty tool is available from Esa where you can simply pass the ID of your Google Spreadsheet and see the resulting map. An example is here or you can simply substiture your spreadhsst's ID to view your data.

You can easily try this for yourself, provide you have a google account, some sample data, and Lat/Long values for your data - this may require the use of a geocoding routine and there are plenty of them out there, many are free! If you need to locate more mashup developer tools see this section in the GISuser repository (toolbox) - the Batch Geocoder may be a good starting point!

Recall, the Google Spreadsheets data API allows client applications to view and update Spreadsheets content in the form of Google data API ("GData") feeds

Other Useful Links:
http://docs.google.com/
http://spreadsheets.google.com
http://code.google.com/apis/spreadsheets/gdata.html
http://code.google.com/apis/gdata/json.html
http://code.google.com/apis/gdata/index.html
http://gmaps-samples.googlecode.com/svn/trunk/spreadsheetsmapwizard/makecustommap.htm