[Merovingian]

Missing Sync just requires your TP to be in ActiveSync mode (uncheck "Enable advanced network functionality"). First time you run it, a windows pops up, don't dismiss it. When you plug in your TP, it starts installing th MissingSync cab file on the TP. Once it's finished, choose what you want to sync and then sync.

Syncmate is a bit odd and weird but works too and they have a free basic version. Now you have to be in ActiveSync USB mode (and "Enable advanced network functionality" MUST be checked) else it wouldn't recognise via USB.

I've used them both (and currently prefer MissingSync) on iMac and MacBook Pro all on 10.5.5, stock T.P.