The student theatre group at my university has an online site that we use to keep track of everything. It's complex--much more so than any google site could be--but keeps track of shows (including cast lists, crew lists, etc), the calender, and our groups inventory. It requires a log-on and each user has a profile, which contains some basic info about themselves as well as past shows they've been in. This system works well, for the most part, but only because we're a student theatre group. We consistently have the same people involved with productions, so it's practical for everybody to have a profile page. Another group I work with has a site that requires a log-in to access the calendar. This is much less personalised (though the site does track who's in SM, LD, etc for an event and info like phone numbers); it's mostly a list of call times, strike times, etc. The downside to requiring a log-in is that we have no public calendar, leading to requests for us to do an event on a weekend we're completely booked for. If you log-in, you can see which weekends we're no longer accepting events for, but that doesn't help the client.
However, we still feel the need to keep it password protected for privacy reasons. That site has personal information (full names + telephone numbers) as well as sensitive information to the organisation (budget stuff, riders, light plots, etc). It's the same thing with the first site I mentioned. We have a google doc where we keep track of the spending for a specific show--it's fine if somebody on carpentry can see how much money was spent on wood, but that's not something we want the public to see.
We find that the main challenge is getting people to sign up, so we usually have a laptop at the first rehearsal to get them to sign up (or an excel spreadsheet, to collect email addresses for dropbox/google docs). We have found that the less information required, the better. We tie usernames to school email addresses, then ask for name and phone number. Once they've created an account, they're able to add more information about themselves, which some people do, and some don't, depending on what they're comfortable sharing.
What I find crucial in terms of alerting people to rehearsals, load-ins, etc is being able to generate an email list. It's very hard to get people to add your site into their daily routine of Facebook, Twitter, etc, but emailing people are general dates and reminding them to check the site for more info has proved successful.
