Can a cleric channel or cast while raging?
Cast: No. However the moment of clarity rage power can let you cast for one round 1/rage.
Channel: I would say yes, but I'm not 100% sure on this one. I know that channeling doesn't ever require a concentration check, so that is very telling.
Hm, I'd allow the channel. Doki's 'old post' has people talking about whether something provokes as a means to see if it requires 'concentration.' Seems like a good metric.
Heck, the cleric could have some kind of alternate channel that fits the theme of raging divine wrath on ones enemies.