Speck clear shell, that's it...A Targus XL City Messenger bag which is big enough to carry (Believe it or not) my MBA, MBP and my iPad + magsafe's and power cord for the iPad.
It weighs a ton when fully loaded up and I very rarely carry all three, but it's good to know I can if required.
Just one - an Acme Made Skinny Sleeve. I chose this sleeve because it's fairly thin yet still protective with some plastic inserts inside the neoprene to protect against minor bumps. I also have an SGP clear skin on my MBA but don't count this as a case, as well as a Radtech Screensavrz cloth.
I got the Twelve South BookBook. A lot of compliments, but it blocks the exhaust fans, so I worry a little bit when I'm playing a game with the case on.
I just have a black/aqua Joli sleeve. I bought two separate cases previously but returned them both since they were too loose (the MBA slid back and forth, didn't like that).
SFBags Waterfield SleeveCase and RadTech ScreenSavrz. I tried the Rearth Verco keyboard cover but it wasn't really what I expected so it is no longer in use.