I don't use the company network, equipment or time for personal web stuff. Everything is monitored and my boss gets a report on every employee summing up the time they were on and what they were doing.
Remember Radar telling about the Boeing site in CA where rather than take games off the PCs they had him set it up to pop-up a warning if someone opened a game?
Don't forget if your boss doesn't like what you're posting on your own time, and with your own equipment he can't legally do anything...but paybacks are a bitch.