We have tested several widgets at PowerHomeBiz.com to make it easy for users to share our content, and tap Web 2.0 sites to increase our traffic. And the tool we love the most — and using more extensively is AddThis http://www.addthis.com/

AddThis is a simple widget that you put into your site or blog, and visitors can bookmark, share or email your content. If you’re looking at a way to get your content into MySpace, Digg, Stumbleupon and other Web 2.0 sites, AddThis is a tool that can help you

What we liked about AddThis is its ease of use. Setting an account is very easy, and grabbing the widget is a breeze. You don’t have to be a techie to actually understand how it works, and grab the code to be put to your site.

The reports are also done almost in real time, and you can find out the URL of your content that has been shared by a user, and what service did the user shared it to.

But of course, it’s not without its kinks:

• You can’t know and track the URLs that have been emailed by users. You also won’t know the email addresses of the sender and the recipient that some email share-to-a-friend scripts can show you.
• There’s tendency to show false positives, and therefore inflated reports (just hope that it’s not 100% inflated reports). A user can click on share to Stumbleupon, but for some reason, the user failed to login to his Stumbleupon account thereby failing to share the content in Stumbleupon. But AddThis will already read the fact that the buttom was clickd on as a success and report that the URL was shared in Stumbleupon
• Sharing blog posts can be a bit screwy. Sometimes the URL will not be reported in your account and instead will show this data:post.title/. This is also the URL automatically posted into the user form, so unless the user removed this message and replaced it with the actual URL then it becomes a worthless share

But even with the above kinks, AddThis is a great tool for sharing your site and helping it go viral