StumbleUpon is an Internet community that allows its users to discover and rate Web pages, photos, and videos. StumbleUpon allows users to web stumbling for the first time
Now you can Stumble outside of the shadow of the mega-corporate overlords at eBay - two years after Stumble founders Garrett Camp and Geoff Smith cashed out and handed their baby over to the ecommerce giant, they've come back with a team of investors and bought StumbleUpon back from eBay. It's pretty exciting.
iGoogle gadgets interact with the user and utilize the Google Gadgets API. Some gadgets developed for Google Desktop can also be used within iGoogle. The Google Gadgets API is public and allows anyone to develop a gadget for any need. iGoogle recently added a new gadget named " What's Popular". It seems to be similar to Digg, Reddit, Stumbleupon. where you can vote the web pages and add content you find interesti