Favorite Druid/Cleric concentration spells

[veven]

I want to build a Skypledged that focuses on concentration spells.
I was looking for some suggestions for your favorite Cleric and Druid spells (at any level).

I have a second question too. Is there anything that would prevent me from using Sonorous Hum and the Guide magic ability of the Spirit Shaman to effectively have three concentration spells going at the same time?

[Urpriest]

With ways to get around the Concentration requirement, I've heard Summon Elemental Monolith is actually decent.

[Seer_of_Heart]

I believe the swift concentration skill trick will let you get a fourth provided you spend your swift actions concentrating.