[Wlug] shared calendar (web-based)?

I have some guys I work with who would like to be able to use a web-based tool to help schedule ping-pong games. Part of the requirement is that the players don't always have a partner and they would like to advertise available times so that someone else is encouraged to arrange a match with them. I already have an old web calendar program, which works, but I'm not very enthusiastic about it. Does anyone have a recommendation of a web tool that will work? FYI, I'm running Red Hat 8.0. TIA, Bill