There are few Windows Sidebar Gadget comes with Windows Vista. However, have you try to find more gadgets? You may reach http://www.microsoftgadgets.com/ , and browse to the Gallery tab and find the gadgets which fits your want. However, they are live.com gadgets if you look carefully.
I found a new site, there are really many gadgets for Windows Sidebar. You may be try to browse there and download any one of them. There are 10 gadgets now, but it may be more when day is passing. If you are sidebar gadget developer, you may also submit your gadget and Microsoft may publish it on that webpage too.