I am very taken with the song “Hey There Delilah” by the Plain White T’s. I want to put together a mix of similar songs of the same type of genre, which I think of as alternative-rock ballads, with just an acoustic guitar, maybe some strings, and a vocal. A similar one I thought of was "Good Riddance (Time of Your Life) by Green Day. Can anyone help me out with other suggestions?
“I Will Follow You into the Dark,” Deathcab for Cutie
“Chasing Cars,” Snow Patrol
“Jenny” Mountain Goats
i hopped on back of the bike, wrapped my arms around you.
and i sank my face into your hair.
and then i inhaled as deeply as i possibly could.
you were as sweet and delicious as the warm desert air.
and you pointed your headlamp toward the horizon,
we were the one thing in the galaxy god didn’t have his eyes on.
“All for You” Sister Hazel
btw, Hey There Delilah is so overplayed at the moment that I have to change the channel everytime I hear it.
Great suggestions, everyone, thanks!
I suspect you are right. I hardly ever listen to music radio anymore, and I have heard it 3 times in the past week! 
Of course Time Of Your Life was my first thought! I don’t know if you are entertaining 80s hair band rock ballads, but wind of Change by The Scorpions (1990). It’s slightly bombastic because it’s about Big Political Events but it is the acousticky kind of thing you might want.
The Sick Puppies are very good “unplugged”. They just played a couple songs on the local alt-rock station here, and were great.
Hey ya (the version by Obadiah Parker, not Outkast).
There’s a version of Catch the Wind by Donovan that’s just guitar and doesn’t contain the instrumental section.
Or Last Kiss by Pearl Jam. That’s one is pretty depressing, but still in a similar genre.
Elderly Woman isn’t exactly the sound I’m going for, but when I saw you suggested it, I had to comment. I just heard that song on the radio recently, and I hadn’t listened to it in a long time. That is an amazing song…Eddie’s vocal performance is brilliant.
Sarahfeena, here is a YouTube home video clip featuring the song The Only Answer by Mike Doughty, former lead singer of Soul Coughing.
(I have no idea who the happy family in the clip is, but there is no proper video for this song, probably because it is only two minutes long and wouldn’t really appeal to the usual media applications.)
If you like that song, you may also like Looking at the World from the Bottom of a Well, or American Car.
How about “O Valencia” by The Decemberists? Great song that tells a great story.
Old School: Simon and Garfunkel: Mrs. Robinson.
“Mayonnaise” by the Smashing Pumpkins.
The first song that popped in my mind was the excellent story song “Rabbit Fur Coat” by Jenny Lewis. Another, more obscure one is “Said Sadly” by the Smashing Pumpkins (first released as the B-Side of “Bullet With Butterfly Wings”).
I don’t know if it would fit in, but how about some acoustic Brand New. I know they have recorded some stuff lighter/acoustic, but it’s not bad. Anyways, I like Plain White T’s, and I like Brand New, figured I could suggest something.
Brendon Small
Yes, one of these is on The Secret Policeman’s Other Ball soundtrack.
It is a bit folksy perhaps, but my girlfriend turned me on to Brandi Carlile’s The Story.
Thanks again for the suggestions, everyone…some of these songs I haven’t heard in a long time, and some I have never heard of! I love being turned on to new bands…this is awesome.