With this widget you can create a free link to your site and it allows you to get some free traffic along the way. Click Here to Create A link You can embed this widget on your Webpage You can put it on your iGoogle Page
Those types of widgets won't do you much in terms of SEO and link building, from the SE's perspective all links will be coming from the site offering the service, that's because that's where it's physical link is. You can spam your way on hundreds of those widgets and still not get anything.