Which options exist for a Macbook air (2010) SSD upgrade?
Actually it's Other World Computing (OWC, also known as macsales.com) that offers 3rd party SSDs for the MacBook Air. They're based on the fairly widespread Sandforce controllers (also used by OCZ). You can find them here.

The only other option I've heard about is RunCore, which announced in May it was going to make a MBA compatible SSD, but as far as I can tell, nothing's been released yet, and it may only be compatible with 2011 and later models.