theres plenty of free counters out there.
you can check hotscripts.com and find tons of them.
if all you need is something to track how many hits a website gets, its VERY easy to write one yourself if you know basic php.
if you want website statistics, such as which pages did this visitor view, and what order they viewed them, how long they viwed each page for etc....and that type of stuff, you want more than a hit counter.
some examples of that would be analog, awstats, bbclone and a host of other good free ones. awstats is pretty good, i dont really like bbclone though. i like having lots of statistics, click paths etc...
so it depends what you need.