http://ngm.nationalgeographic.com/Alaska would be a good place to possibly release several "un-extincted" species like mammoths and latifrons bison. Alaska has had some success with reintroducing woodland bison and has the space.
While we are waiting for scientist to successfully clone extinct species though there are species currently going extinct that could be given a new lease by being reintroduced into Alaska like the saiga antelope:
http://en.wikipedia.org/wiki/Saiga_antelope and possibly even lions. Bear gun lion gun - what's the difference.
I am not sure whether the short faced bears or passenger pigeons scare me more. Our grandcestors might have killed both off for good reasons(?)