Judging by the number of online timers available on the Net, many people like to keep a close watch on their modem and ISP connections. One timer that may suit your needs is Christopher Heng's LogTime, which you can download from http://web.singnet.com.sg/~cslheng/ltdl.html or any Tucows site.
LogTime is a utility that tracks your online time and keeps a running total of your weekly or monthly expenses. It supports numerous payment plans, including flat rate plans, those that have different rates for different times of the day, and those that incorporate blocks of free connection times each day or month.
LogTime is smart enough to detect and log modem connections automatically, and if you use multiple ISPs, it can tell which one you've called. You can keep tabs on your modem by configuring LogTime to alert you each time a connection is established, and if necessary, you can print out the log of all your connections. LogTime is available for Windows 3.1, 95, 98, NT (see our cover CD), and Linux, it's easy to set up, has great documentation, and best of all, it's free.