This counter is relatively basic, however it has some neat features such as font size, color and face options, line breaks before and/or after the count is displayed, center the count text and hide the count as a comment in the HTML. This script works on multiple pages with a single data file. It uses SSI (Server Side Includes) and includes a .htaccess file in case your server does not support SSI.
GTCounter is a counter script that can show the overall number of visitors and the number of visitors currently online at your site. The counter can be added using SSI, as a frame or from a different script. Includes the ability to block IP addresses, different templates possible.
AAA Contador is a very good counter script written in portuguese. It has many functions like IP log, Date log, Add and Reset counter, easy to install (only one file has to be modified) and requires SSI.
This counter program written in Perl keeps track of the number of hits made to a website. It uses file lock commands to ensure that the counter data does not get corrupted when two users simultaneously access the website. Requires Server Side Include capability.