How odd. I've tried with both apps and it works with neither. I connect using PC Suite Mode and tell iSync to do its thing and with the community app it can't find it over bluetooth and with the Nokia one it never connects....it says "connecting" then just gives up.

Got it all working again. I removed the isync plugin for USB, deleted the isync preference file & the Bluetooth preference file, restarted my computer & N900 then installed the community supported Bluetooth plugin & did a sync. Ahhhhh.

Somebody wrote a plugin for iSync for the N900 (google it). It works fine! But if you have the same No. twice with separate (or different) names in your N900 contacts, when you receive a call from that No. the phone won't report the callers name!

It finally worked!!!!!
Cleared out all N900 plugins from Mac HD/Library/phoneplugins.
Updated software
Downloaded the community plugin and installed it

and Voila after many months of trying it just worked!!!!

Thanks to all on this forum who have developed the software. I can now keep the phone!!!!!!

I think you talk about this...

http://n900isyncplugin.garage.maemo.org/

N900 iSync Plugin

Hello, fellow maemo fans. For a while I have got this marvelous computer with telephone abilities called N900.
Due to the fact I use for more than two decades Macs, one of the greatest demands to functionality is a smooth integration within the Mac environment. There are two iSync plugins so I thought and the Maemo/Linux is somewhat related to the deeper engine of the MAC OSX there should not be any trouble.
SO IT IS!!!
For a start: Forget iSync! Completely undocumented but PERFECT working is the following procedure:
Make your different kind of calendars (names according of the purpose with different colors etc. eg. privat, holidays, business, moon, etc) with iCal on you mac (OSX 6 in my case).
Then mark the kind of calendar you want to have eventually on the calendar provided with the N900 on the left side of the iCal window. Then export this calendar. Do so with all the different kinds of calendars you want to export. All these calendars will have the suffix .ics. You can add also other calendars provided eg. by http://www.sunbird-kalender.de/extension/kalender/
(German holidays etc).
Then send these files via USB or bluetooth to you most loved gadget, the N900.
Here open the Filemanager choose one of these .ics files and "open" it. You will be ask if the containing data should be integrated
inside an existing calendar or if you want to create a new one. If you do so ALL specialities as eg the color will be shown by the Nokia app as well. So eventually you have an exact copy of the same appearance you are used to have on the MAC.
iSync can NOT do this. It can only merge all different calendars from iCal into a single one on the N900.
Export of the OSX adressbook follows the same pattern.
Enjoy your N900 and be grateful for the wonderful Maemo community and DO donate for the good Apps you use!!
BTW: I think the decision by Nokias new CEO and former Mirosoft man to introduce Windows as the "new" platform is not only a waste of resources and promising, open ways, but more a stupidity: For a long time Microsoft has NEVER achieved even a half way proper working mobile system. (as they never had a really nice and clever system on desktop computers as well ...)
So I hope the community and some very good programers will keep our N900 fresh and "state of the art".
There is yet not better, more open and technical more sophisticated mobile tool, - not even in sight. The N900 is made for those who know and not just consume!

Is there still development on this. I've just got an N900 and am syncing it with OS/X 10.7 (Lion) using iSync. I've had to fiddle my OS/X contacts a bit, but it now works perfectly - almost.

The one feature I need added is the synchronisation of Skype fields in Contacts. Both OS/X and the N900 have Skype fields, but they don't synch.

The documentation says VOIP and IM fields aren't supported. Is this something that can be fixed, or is it impossible?

I'm certainly not working on it anymore, I have an HTC Desire S now. If you're feeling adventurous you can get the source code though and have a bash at it with the iSync Plugin Maker if you download the developer tools from Apple.