Grand Stream

Last Exile on the Funimation Channel 

Last Exile: Fam the Silver Wing on Funimation Channel

Notes: I think you can only watch each episode once without some kind of subscription or something, but it's a really good way to see the official subs, and watch the dub of the first series if you don't have access to DVDs.

Last Exile on Hulu (only  available for US audiences)

Last Exile: Fam the Silver Wing on Hulu

Edited to add Hulu links and request that if anyone knows non English or just sites outside US/Canada legally airing dubs/subs of Last Exile, Fam or both online I would greatly appreciate  links to add to the post.

Other Countries

Australia
Last Exile: Fam the Silver Wing