Here's a list of songs for mothers or songs about mothers, in no particular order. I've avoided lullabies (songs by moms, typically), as well as songs about general parentual units, or songs about moms and dads.
If a song isn't on the list, it's because of one of the three "O"s: Oversight (I knew about the song and just forgot), Omission (I knew about the song and chose to exclude it), or Obtuseness (I didn't know about the song at all). I expect the third category to be fairly large, so feel free to add your suggestions in the comments section. And most (if not all) of these CDs are reviewed here, so if you're not familiar with a CD, look at the review sidebar to the right.
(By the way, Fran had the same idea and got there first, but between the two of us, I think we ought to come up with a decent mix CDs.)
"Mama Don't Allow" -- numerous versions; try Brady Rymer's version off of Every Day Is a Birthday
"Mama Hug" -- Brady Rymer, Every Day Is a Birthday
"Mama Is Sad" -- Justin Roberts, Yellow Bus (it's a song about divorce, so I'm guessing it's not gonna go on too many mix tapes)
"Five Little Ducks" -- try version on the Old Town School of Folk Music's Songs For Wiggleworms
"Thank You Mommy" -- The RTTs, Turn It Up Mommy!
"The Coffee Song" -- Ralph's World, At the Bottom of the Sea (not really about moms specifically, but it was the first song that came to my wife's mind when I mentioned the topic of the post)
"Hush Little Baby" -- try version on the Old Town School of Folk Music's Wiggleworms Love You, though it's just as often that Dad is the person buying baby that billy goat
"Mother and I" -- Bill Thomas (and a Circle of Friends), Time Can Be So Magic