There are a number of services that rank web sites. I find that I check alexa.com here and there. So as you employ various techniques to make your site better, you can check back and see the long term impacts of how these efforts impact your ranking.
You can also see demographics of visitors.
And you can see geographic data as well.
There are other better sites, with far more detailed information such as Google Analytics. But a very top-level, upper level view of how your site is performing is something like Alexa.com. Nice and simple.