If you're planning to upgrade the SSD in your Macbook Air, here's a neat little idea from Other World Computing: stick the old drive in a tapered aluminium case to provide an external drive which matches your laptop.
OWC offers the Aurora Envoy enclosure kit for £12 when you buy any of their Mercury Aura Pro Express SSDs. The enclosure, which weighs 42g empty, is made of aluminium and has the same taper as the Macbook Air. The drives come in two speeds, with the 3GB/s drives suiting the 2010 Air and the faster 6GB/s drives only working with with 2011 Airs. Prices are so-so: £160 for 180GB of 3GB/s storage, say, or £500 for a 6GB/s 480GB drive (there are plenty of other options in between, of course). You can also buy the enclosure kit alone for £30. OWC ships internationally. [OWC via Engadget]