Backlinks is an important element of any SEO strategy. How do you check how many backlinks you have. And how do you see how many different domains link to your site?
You can use the available services from for example Yahoo!. But the problem I see is that you cannot see easily from how many different domains you get backlinks.
The best tool I have found for this is:
I believe you can use it only once per 5 days or so to check the same domain, but that is fine.
Try it out and let us know your comments what you think.