The third part sync apps, in my opinion, are a waste of money. Snow Leopard builds in some really awesome sync services for outside servers. If you're using an Android, you have to love your gmail account first of all. Everything Android is synced this way. For your calendars, you will first need to make sure calendars are enabled on the Gmail side. Just login, choose calendars and settings and your good to go. On your Mac, go to iCal>System Prefs>Accounts>+ to add an account and choose Google as the account type (automatic screws up your sync). Login and Google calendars shows up in your calendar list on the left. There is support for multiple calendars, but they need to be created in Gmail. iCal recognizes these as Delegates. You'll enable Delegation in System Preferences for your Gmail account. Address Book works the same way, System Preferences>Accounts>Google and sign in.
I have an Android (HTC Desire) and this method works great for me. Sync is virtually instantaneous.