MacBook Air. Check.
SSD upgrade. Check.
Now what do you do with with the original 64, 128 or 256GB SSD blade that you just removed from your MacBook Air?
After you upgrade your SSD, you'll have a smaller one leftover that looks like this:
A lot of professionals that use a MacBook Air as their primary machine will find themselves upgrading the stock Apple SSD before too long. It's just not possible for people that are used to spacious and cheap spinning winchester discs to whittle all their data down to 64, 128 or even 256GB -- making an SSD upgrade inevitable.
After getting a larger SDD for my MBA 13 (I opted for a Mercury Aura Pro Express from OWC) I found myself with an expensive Apple SSD blade that I didn't know what to do with. Rather than simply sticking it into a drawer, I recommend picking up an OWC Mercury On-The-Go enclosure ($70, below) which acts as a surrogate home for your older, smaller SSD.
It looks exactly like OWC's standard On-The-Go enclosure -- which I've used for years -- except with a small daughtercard that adapts the standard SATA connector to a smaller ZIF 40-pin interface for the MBA SSD. Once installed the old SSD acts like a normal external disk -- albeit a fast one.
So there you have it. Don't relegate your MBA SSD to a drawer when you upgrade. Put it to good use in an external enclosure from the folks at OWC.
Update: If the clear, lucite On-The-Go enclosure isn't your cup of tea, OWC's Mercury Elite Pro mini ($110) enclosure also accepts a MacBook Air SSD.