Starting in early 2013, we'll be turning off Gadgets in Google Spreadsheets. For more information, see our help article.
If you're having trouble using one of the new gadgets, take a look at some of the samples found below. If you're still having trouble, try posting your question in the Google Docs help forum.
Interested in creating a Gadget of your own? Check out the Google Gadgets API and the Google Visualization API. For help using these APIs check out the Google Visualization API forum and the Google Gadgets API forum.