Microsoft’s Mobile syncing service - My Phone has just entered Public beta. Users can sign up for Free by installing My Phone on their Windows Mobile 6.x phones and signing in with their .NET Passport. My Phone service will Sync your SMS messages, Contacts, Notes and Calendar online just as Microsoft Exchange. However, My Phone only syncs between 5 AM to 11 PM (unless you sync manually) and is not always active like Exchange.
For more information on My Phone, you can refer to this post.