ScheduleOnce is a simple web 2.0 service that helps you to schedule meetings with accuracy across all time zones.
You can specify time range and date range for your scheduled meeting. You need to specify your time zone while creating your schedule. You can give permission to suggest time zones by other invitees, or you only suggest. Once you create a schedule you will get a unique URL, just send this to all your clients so that they can access your schedule and modify the time zones if necessary. Your invitees can leave messages to you and you can reply to them.
There is no registration and logging in, just create your meeting schedule right away and send the info to all your mates. It is definitely a useful app with simplicity and nice functionality.