I've been using NuevaSync to sync my contacts with my google and plaxo accounts. This guy gives a nice tutorial that uses google, plaxo, & thunderbird..
http://www.tipsfor.us/2008/04/19/syn...ogle-for-free/
Really, the NuevaSync
http://www.nuevasync.com/ is all you need. Oh and you dont have to install anything on the phone!