Philippe Legrain, a blog largely devoted to defending the merits of immigration, and associated phenomena such as free trade. Issues he has spoken about and published on extensively. Various people for various reasons may wish to deny the association between the two, but arguments about free movement of goods and free movement of peoples have common moral and economic aspects. The worst tyrannies have always strongly restricted both, something opponents of open immigration and of free trade might like to ponder.
Legrain, now London based, has worked in financial institutions, financial journalism, academia, book writing, thinks tanks, transnational institutions and think tanks. He describes his outlook as economically and socially liberal, and as far as I can see he takes that in a centre-left direction. For example, he is associated with the magazine Prospect which is very oriented towards New Labour. The kind of social democrat who has classical liberal/libertarian tendencies.