OVI.com [1] is Nokia's set of web services, including among them complete PIM data handling and synchronization with phones via SyncML. Formal interoperability testing [2] has not been done yet, but a user of SyncEvolution 0.9.1 reports that it works for him. Getting the necessary setting information for SyncEvolution is a bit tricky, so check out his nice report for a step-by-step guide [3].