Although there are new widgets popping up every day, there are some clear leaders who are setting the bar in terms of development, innovation and success. Here are a few from the many that I think are doing it well.

Tripadvisor
When you go to the tripadvisor site, the directions and value proposition to downloading its "cities I've visited" widget are simple, but the functionality and buzz factor of this widget is off the charts. "Where have YOU traveled?" asks the widget. Create an interactive travel map to share with your friends and help them plan their trips. Nearly everyone I know is using this widget -- from my teenage cousin to my 60-year-old father-in-law. I can't wait to plan my next trip… nice job!

iLike
If you're on Facebook, you've heard probably heard of iLike. In its words, "iLike lets you add music and videos to your profile, dedicate songs to your friends, and see who's going to what concerts. Bonus: get free MP3s matching your tastes, and beat your friends at the Music Challenge." 

The bottom line is that this popular widget makes it even easier for people to do what they already like to do anyway -- talk about what music and videos they like most, learn what favorites they share with their friends, test their music knowledge, and, of course, share content and dedicate songs. It's easy to get started, the value is clear, and it's completely relevant to the target audience. No wonder it's been a huge success.