LITODELOSREYES  Snow Leopard does have google contact syncing but it still doesn't work for me. My last name and many people in my address book have spaces in their last name and google mangles these names. Google sees a name such as de la cruz as cruz and dumps the de la into the middle name spot. I've run into a couple problems, sometimes google contacts such as this will sync back to my snow leopard address book as a new contact or it will just reformat the name. So...Spanning Sync is still a needed app for those people who have issues such as these. Somehow Spanning Sync works around these issues.  
(Version 3.0.2b)

WUDDEL  Snow Leopard's iCal can now talk directly to Google Calendar ... just to let you know.  
(Version 3.0.1)

THEFLEE  Works great with android.

Really a match made in heaven.

I love this program, and although there a some other alternatives out there this is the best. The program is free if you get 4 referrals! and nothing is better then that.

http://spanningsync.com/?r=7EBTXF

to save 5 bucks!  
(Version 2.1.3)

PICKLESS  sorry for the double post, I 'replied' instead of 'reviewed' :(

I used v1 and hated it but I've just upgraded to v2 and have to say it is pretty sweet!! I love the gmail contact sync, very slick.

price is still a little bit up there but you can get it for less with a discount code. I used GTMFRU and got $5 off so I only paid 20 bucks which seems about right to me for this tool.   
(Version 2.0.2)

ASPARTAMEMSGSUCK  No question that this is nicely implemented, but the price is not warranted. Have been testing BusySync http://busymac.com/index.html and I have to say I am more than happy with it AND the price!  
(Version 2.0b352)

NIGEL SMITH  Google Calendar CalDAV support

ical now syncs with google calendar.

check it out: http://www.google.com/support/calendar/bin/answer.py?answer=99355

No longer any need for this and the ridiculous yearly subscription costs

I am a current subscriber and am not sad to say bye bye.  
(Version 2.0b349)

CHADCN  Per comments regarding Plaxo and icalx.com

Plaxo only allows one-way syncing and it will only sync one calendar to Google cal. If you have several calendars, like myself, Plaxo is worthless.

Getting icalx to actually display calendars is hit and miss, which means getting them to google cal is the same. I would much rather use something that provides direct syncing to google cal and not have to go through the trouble of learning another service to be used as a middle-man, which plaxo and icalx are.

Spanning Sync is the best at what it does, has been rock solid and consistent, and for me is well worth the money  
(Version 1.2)

GHARTNESS  Or, sync to icalx.com, then sync that to Google Calendars. It's very easy and very free.  
(Version 1.2)

MACMANIA  You can use plaxo to sync iCal, Gcal, Address Book, M$ Outlook, etc. Oh did I mention for FREE?

www.plaxo.com  
(Version 1.1.4)

CHRIS MUENCH  The software works great. You just set it up and forgot about it. The 2 way syncing works great just as expected.

I use gmail apps and have 3 calendars (Personal, Work. School) and it is exactly what I needed.  
(Version 1.1.3)