When I'm on the road, especially abroad, it isn't convenient to transport a full blown hub around especially with the power bricks they generally require, but I still want to harness USB 3.0 and Ethernet capabilities normally provided by the hub.
The Kanex KTU20 Thunderbolt adapter is an ideal compromise to solve the problem. This little black box plugs into the Thunderbolt slot on the MacBook Air and adds a USB 3.0 port and a Gigabit Ethernet port to enhance the MBA capabilities. The adapter is about 5x8x2 cm and weighs just 91g.
It's not a particularly cheap solution - it'll set you back about £75 - but it is compact and it doesn't require any additional power cables. I used it most recently on my 7 month stay in Prague where I used it to connect to the apartment's router and the HGST Touro Desk Pro 4Tb USB 3 hard drive I took with me. By combining this with a 7 port USB hub I had access to all my USB requirements (albeit running at USB 2 speeds but none of these devices were performance critical).
The Kanex KTU20 will stay packed my travel bag - it's ideal for short trips involving hotel stopovers. It's just a shame it doesn't have Thunderbolt pass-through capability...but now I'm just being greedy!