Free Counters

1. Google Analytics - By far the best free service online. Actually this service cost $199 before it became free. It gives any statistics you may need and even more.

2. Statcounter - A good real-time counter. You have detailed information on visitors of the last 500 page views. You can make projects for each of your site also you can choose to have a button displayed on your site or not (invisible). Spite the limit of 250.000 pageloads/month for the free account it's still a very good counter.