Gadgets are being developed & added to Google every day, as well as some of them being dropped.
To insert a Gadget onto your web page:
1.) Edit the page where you want to have a Gadget
2.) Cursor to the location on the page
3.) Click the Insert
4.) Scroll down to More gadgets ...
5.) Scroll or Search for a gadget of your choice
6.) Click OK to have it put on the page
7.) Click SAVE to save the changes and review the gadgets
Note: To see more Gadgets - click Public (Selected is what shows by default)