2008 MacBook Air connected to a 2011 iMac from DVI to Thunderbolt? I have an original 13" MacBook Air from early 2008 with a micro-DVI interface and a 2011 27" iMac that I would like to use as a monitor for the MacBook Air.

A cable that converts the micro-DVI to a DVI connection came with the MacBook but of course there is only a Thunderbolt display on the iMac and I would like to know if there is (officially or un-officially) a cable that will go from DVI to Thunderbolt so I can work on my MacBook Air and see what I am doing on my iMac please?
You should search for a DVI to Mini-Display port, as Mini-Display cables are compatible with Thunderbolt ports. A quick google search turned up this  from the apple store. Be aware that this is a DVI-D adapter, which means it only outputs digital signals.