At DrupalCon DC they pronounced it like "eager".

Aegir (pronounced /ˈaɪ.ɪr/ EYE-irr) @ http://en.wikipedia.org/wiki/Aegir_(moon)

Looks like it is similar to the english word 'ire'.

Yup! It is pronounced "Ægir"

The norse language is dead, and no one knows how it was once pronounced. But being a Norwegian myself and somewhat interested in norse mythology, I've looked at a Norwegian Wikipedia article on norse phonetics (http://no.wikipedia.org/wiki/Norr%C3%B8n_lydl%C3%A6re) and come up with a small pronounciation guide for English speakers.

Æ is like the E in Egg.
G is hard to explain. A soft G, but not like the G in Gin. Think back of the tounge.
I is like the E in Me.
R is a rolling R.

"E-girr" if you like. Then I came across a website claiming the Æ is to be pronounced like the English word Eye, which would make it "EYE-irr". That variant is close to modern Icelandic pronounciation, but it's understood that modern the Icelandic pronounciation has changed a lot since old norse times, so I'm not so sure that's how they would have pronounced it. In other words, nobody really knows :)

I pronounce it in Norwegian, similar to my pronounciation guide above, except with the Æ like the A in Man.