Akonadi-googledata allows you to syncronize Akonadi with your Google calendar and contacts. Passwords will be stored in KWallet, for while only 1 account is allowed. For hosted accounts (i.e. joe.bar@whatever.com), just input the whole username plus server name in configuration dialog (i.e. joe.bar@whatever.com). For normal google accounts (i.e. joe@gmail.com), just the username is required (i.e. joe). Only the main calendar is supported. Recurrent events are not supported, the reason: Google uses an invalid iCal inside of the XML to represent recurrence). http://code.google.com/apis/calendar/data/2.0/developers_guide_protocol.html#CreatingRecurring
WWW: https://code.google.com/p/libgcal/