One way to monitor web services is to enable logging in IIS. (I'm running IIS 5.0): To enable logging, select the desired PC from the tree-view list in IIS. Select the 'Web Sites' folder, then righ-click 'Default Web Site', then select Properties. In the last panel, check 'Enable Logging'. Then, click the 'Properties...' button and select the Extended Properites tab. Whatever you choose here will be in your log. By default, IIS puts the log files under your windows directory. For example, I'm running Windows XP Professional and my log files are placed in c:\windows\system32\logfiles\W3SVC1. (You can select the 'General Properties' tab to see where your default path is for your log files). Keep in mind that the times recorded in the logs are Universal times. (You can change this using the 'General Properties' tab, too). The logs always start at midnight.
I hope this helps!