Recently, I was putting together a collaboration call to prepare for a panel I moderated at an industry event. There were 4 of us - three in Europe, me in the US - and we all used different calendaring systems so it was challenging.
Doodle: A great tool for cross-platform, complex scheduling
One of the panelists introduced me to a great tool to help us figure out what times worked for everyone. It's called "Doodle" and it makes it easy to present various schedule options. You can either enter the information manually, or start with your availability from your Google calendar so it's pretty easy.
You then invite others to weigh in on their preferred time, and they see a form that looks something like this sample:
You can see people's updates and preferences as they fill them in, which is very handy to make sure you aren't heading for a train wreck.
Doodle is for more than just calendars
Doodle also allows you to create quick & dirty polls and send them out to large groups to provide feedback. Doodle even provides a "None of these options works for me" button.
Doodle's polls aren't anonymous, so they may not work for every situation, but I've used them for things like figuring out where people want to go for an outing, and what kind of food people wanted for an off-site meeting.
Doodle's also free, so check it out.