I use the wonderful application Omnifocus by the Omnigroup. I use it at work to keep track of projects and I use it at home to keep my other things together.

I've been longing for .Mac syncing, but I recently discovered in the general preferences, you can change the location of the database. Set it to a folder on your iDisk, and set your iDisk on both machines to sync automatically and there you go!

Warning this is kind of a hack, while sync services should prompt you for a discrepancy, just be careful and make sure you don't leave both machines running with the app open.