I bought the griffin esata expresscard to connect esata external drives to my 2010 macbook pro with snow leopard but the driver which was included wouldn't install. Luckily I downloaded a driver from sonnet and it worked:

The driver I used was 1.2.6. The expresscard is less than $30 and seems to work. My plan is to use the seagate goflex thunderbolt adaptor to transfer footage from the ssd to my esata external drive connected to the expresscard.