You have your calendar and I have mine and nary the two should meet. That works some of the time, but if you are working on a project or have a business a shared calendar helps keep people connected.
Domain-Box Shared Calendar offering is pretty good. The price is even better at $12.99 a year for up to 5 people to have group calendar access. Unlimited people for $24.99
It works with smartphones too. Here are some of the features from their marketing page
Boost productivity by having one central schedule updated in real time.
Changes made by any one member are instantly visible to the entire group.
Easily check others’ availability before planning meetings or events.
Quickly reserve shared resources, such as meeting rooms and laptops.
Delegate control, choosing which members have administrative access to which Calendars.
Share documents and files with members of the group.
Task Sharing feature keeps group projects moving forward.
Our Calendar sends and receives meeting requests to/from Microsoft Outlook® calendar.
Integrates seamlessly with iCal® and iPhone® calendars.
Synchronize with CalDAV devices and applications, including iPhone, iPad®, and Apple Mac OS X iCal®.*
Use Calendar with other mobile devices or calendars by importing, exporting or subscribing to calendars.
Check your schedule anytime, anywhere you have an Internet connection.
Quickly add a new event or task using the easy Drag and Drop feature.
Color code your events – one color for your weekly staff meeting, another for your son’s soccer games.
Create your own task list; set start and end dates and track tasks to completion.
Invite others to meetings or events you schedule (works with all standard calendars).
Get reminders via email, text message, or screen pop-up.
Allow attendees to invite others to your events (optional).
Add attachments to your tasks and events for all-in-one organization.