I ran into a great free resource the other day. It is aboutus.org. it was originally a site where they collected info on websites from their About US page (hence the name). But it has some really cool free tools. It has a home page analysis which will help you make your homepage more search engine friendly and it also has a web presence report that can tell you how you online presence is fairing. For example:
http://www.aboutus.org/Website.ws#web-presence- The website.ws page has 159 backlinks on google and 3607 on alexa. It has an Alexa rank of 5764. They have a huge presence in google groups, and no presence on digg.
I gave a detailed rundown in my blog which is linked to my profile but if you are looking for a simple seo tool that doesn't cost anything give it a shot. Your site may not be on there but it will find it and rank it. This isn't an affiliate program and I get no compensation from this, it is just a cool site I ran into the other day.
Hope this helps
tony