monline

"PRTG Network Monitor is the powerful network monitoring solution from Paessler AG. It ensures the availability of network components while also measuring traffic and usage. It saves costs by avoiding outages, optimizing connections, saving time and controlling service level agreements (SLAs)."

I was looking for a free solution to monitor the uptime of an internet connection (using a Windows PC) and stumbled on this one. I admit it's a bit more than I was looking for, but there're not that many free utilities for network monitoring so grab it while you can. The freeware edition handles at most 10 "sensors" (ie. you can setup monitoring of 10 network resources). For monitoring the uptime of your network connection you need only one, so it's more than enough.