Weddingbee boards

My oldest friend (literally -- we grew up across the street from each other since we were born!) has an amazing voice and is going to sing a solo during our Lutheran wedding ceremony.  The song doesn't have to be religious, but it does need to be church appropriate.  My friend is a mezzo soprano and is open to singing anything -- which is great, but that means it has been difficult to get any suggestions from her since she's trying to be flexible and is telling us that whatever we choose will be fine. 

I am at a complete loss and I don't even know where to begin looking.  Does anyone have any suggestions?  Religious or non-religious?  I'd love to hear what you all have chosen for your soloists!  Thanks in advance for your help

Thanks ladies, I will have to look these songs up!

I was asked by a good friend to sing in her interdenominational outdoor wedding and sang 'Come Away With Me' by Norah Jones.  Then a couple years later another good friend asked me to sing at her wedding and she picked 'Grow Old With Me' - both were appropriate and very pretty.  And not very difficult to sing (I'm no pro!)  Good luck!