As an alternative for those who do not have access to Microsoft Exchange there is another alternative that we use which is proving very worthwhile. We have our own mail server but use MDaemon so we did not want to go the Micsrosoft Exchange Server route being a small company.
Instead we added an Apple MobileMe subscription for AUD $119 pa and that allows us to synchronize our calendars across Outlook on the Windows office environment and the iPads and iPhones out in the field.
We tried the Google applications but there were too many quirks and the Apple solution has worked just fine for us.
I agree with the Dropbox solution and that works really well for file transfer etc. Another app that we use to great advantage is Evernote which also synchronizes across the whole array of devices.