GooSync uses something called SyncML or Synchronization Markup Language to synchronize your mobile device's calendar with your Google Calendar. The SyncML is an open standard, so theoretically it should continue to work regardless of any upgrades on Google's end. Basically, your phone or other mobile device connects out to the Internet using its normal method. Once there, it contacts the GooSync Servers which then connect to Google's Servers where your calendar is stored. If you are paying attention, you see that there is a bit of a trust issue here, but GooSync uses Google's AuthSub process which means that your data never passes unencrypted through the GooSync Server.
Of course, this requires software from GooSync for which you will need to register an account at GooSync. The good news is that the basic version is free. The basic version only does your calendar. If you want to do your Contacts and Tasks too, you have to shell out for the upgrade (or find other software for that piece).
Once you've created a GooSync account, it is time to download the software. There is one catch. Make sure you get the right version of GooSync for your Windows Mobile device. There is a touch screen version, and a non-touch screen version. You pick your phone or device from a list- and hopefully it gives you the right download.
After the standard installation process, configuring GooSync is relatively simple. First you choose whether you have a personal Google Calendar, or a Google Apps Calendar. If you don't know what I'm talking about, you have a personal Google Calendar. Once you've logged in, a page from Google pops up to inform you that the good folks at GooSync are asking for access to your account on your behalf. You grant access and then, GooSync is in, and we are in business.
Make the authentication process a lot easier on yourself by logging into your Google Calendar that you want to sync first. Just open a new tab in your browser and login to your Google Calendar the standard way. That way, when GooSync asks for permission to sync, Google will come to you and ask based on the fact you are already logged in. If you are like me, and you have more than one account at Google and you are logged into the other one, you can get crossed up.