13" Air as my main machine.
2010 Mac mini as a backup/media server.
12TB+ connected to the mini for storage and redundant backups.
Carbon Copy Cloner for hourly backups over network to the mini.
4-year family account with
CrashPlan ($287 for 4 years or $6 monthly for unlimited storage from up to 10 computers is a small cheap-ass price to pay for security against fire or flood.) for online backup and access to all files on both machines from anywhere, including my iPad and Android phone.
Plex Media Server on the mini serves up my ripped DVD's.
Plex app on OS X and iOS for watching my served media from anywhere.
Parallels app on both machines and Parallels iOS app on my iPad for controlling my virtual machines and computers themselves also from anywhere in the world.
Free DropBox account and Hazel are used for automated transfer and organization of files I don't need to keep on the Air, and having them on my internet backed up server drive means I can still access them from anywhere with apps for OS X, Windows and iOS and Android I'm set. It's a good age to be living in.
I run everything on my Air. Including light gaming with Steam. Duke Nukem Forever (Only used as a graphics example) runs pretty well, and Portal 2 is just fine. Not the best, but playable. Other games run well too.
Basically I have embraced the cloud. And no, I am not being paid to advertise for anything. These are what I use because they are the best you can get when you do the research. (There are alternatives to CrashPlan including Mozy and Carbonite, but their prices are terrible in comparison and don't have the same "unlimited storage forever and ever guaranteed" guarantee CP has. Mozy just recently dumped their unlimited plan and raised prices. And Carbonite doesn't even have a family plan!) I just like to type a lot of words. So sue me.