Hi,
I've used Squidoo for link building before and it does provide a good backlink.
You need to make sure that your article is live on Squidoo before the link is seen by the search engines. This isn't easy, but it is possible.
Firstly, make sure your post is worthy of being published. Make your lens as interesting and unique as possible - lots of content, images etc. Squidoo seem to love 'top 10' articles.
Secondly, make sure your article is live. Squidoo will often put your post live at first and then take it down over the next day or so. This can be rectified by building links into your squidoo page (ie plug it on a social network page like Facebook, or build some free directory links into it).
Another site similar to Squidoo is 'HubPages', this is good for link building as well.
Hope that helps!