I recently discovered the blog Leave the Lights On when I got a link from there. Perhaps I shouldn't say this, but when I first went there, I thought it was a splog due to the layout, but it's got legit posts, some of them quite good.
In particular, I draw your attention to the post "Can You Believe in Aliens if You Are Catholic?" The blog's author, who goes by the name Ginko100, puts it well when she writes, "To the typical Catholic, this question is not even very interesting, let alone important." That's about how I feel, though I did earlier attempt to argue that extraterrestrials, when and if encountered, would be able to receive the Sacrament of Holy Orders.
Also check out her series "Aliens and Origins."