Have you tried Google Calendar or Google Docs yet?  If not, you should check them out.  You can get there by clicking on http://www.google.com/apps/.  Google, as part of their desire for "world dominance", has brought forth some great tools for online collaboration, including a web-based calendar that you can share with those you deem appropriate, and a document management platform in which you can share all types of documents. 

We find these tools to be great ways for people to collaborate.  These are cost effective (free is good) solutions to situations in which groups of people seek to coordinate schedules by sharing their calendars, and want to share documents.  As a web development company, it is more important that we find cost effective solutions for our clients rather than find and/or build a custom solution.   We have found this to be the best way to retain clients for the long term. 

If you have a need to share a calendar with other people, check out Google Calendar.  If you get frustrated emailing attachments around the world, modifying them and having several versions saved on individual computers, check out Google Docs.  All it takes is to sign up and remarkably, there's no fee.