I often use the Alexa traffic ranking tool to get a rough idea of how active a website is, and how it's activity is changing over time. I've not installed it up to now, mainly because of a few scare stories about compatibility problems, and also that my antivirus tool gives persistent warnings about it (it is classified by some as adware, or a "potentially unwanted program" or PUP). However, as I often refer to Alexa.com in a typical day, the advantage is considerable, so I have taken the plunge and installed it. The immediate impression is that everything is fine.
Alexa - Alexa Toolbar