I spent a fair bit of time looking at groupware packages for a non-profit that I help support. I ended up going with PHProjekt - not too bad to set up and the non-techies in our group don't have any problems with it. I've not yet worked with the scheduling pieces, but the rest of pieces that we've used have been easy to use.
One more thought: WebCalendar.
http://webcalendar.sourceforge.net/
Project of the month recently at SourceForge and I will be evaluating it for us soon; never used it yet, but looks great for what the OP needed.
-- Rodolfo J. Paiz rpaiz@xxxxxxxxxxxxxx
