I just wanted to add this as a topic and write what I've done but maybe you have some solutions that are better than mine. I have a Dell Desktop PC at home (mostly for driving our television & various media). I have a 17" MacBook Pro & a new MacBook Air. I wanted to keep files, folders, data in sync. Time Machine would work but my MacBook Pro has a very large drive so it won't all stay in sync. MobileMe: I bought this for contacts, calendars and general simple syncing of things. I'm not happy with iDisk and Apple's Backup application so... SugarSync: $49 dollars a year for 30Gbs of storage. Sugar Sync is installed on my iPhone, PC and both Apple computers. my 17" MBP is my primary machine so that's the host and all of my docs, desktop, downloads and some /Library/Application Support files are sent to their cloud servers. My PC & MacBook Air download those and upload changed files. The whole system works well and the first sync took about a day. This isn't an advertisement but I did have to do this to keep everything in sync and effortlessly. Do you guys have any tools that you use to sync your Macs and Windows machines without any effort at all?