Churches

this website has English information about Lutheran church services:

http://www.kirkjan.is/english

this is about Catholic services:

http://www.catholica.is/k.html

There are also occasional services in other languages than Icelandic and English, particularly around high holidays. I've been to a German service, for example.

however, if you're moving here for a while, I do recommend the Icelandic services as it's a very useful way to learn the language and meet some locals.