I think "Forever Young" by Rod Stewart makes a good slide show song. I played it in the senior slide show at my high school yearbook party right before graduation and even the guys were in tears.
"These are Days" by 10,000 Maniacs is always a good one.
"You Ain't Never Had a Friend Like Me" from Aladdin! 
"You've Got a Friend" James Taylor
"Lean on Me" or "Stand By Me"
"Feels like home" by Chantal Kreviazuk is good as someone mentioned above.
Another good song that is also from Dawson's Creek and has lyrics similar to "feels like home" is "Never Saw Blue Like That" by Shawn Colvin. I think Kappa uses it a lot because of the blue references.
Never Saw Blue Like That 
Performed by Shawn Colvin 
Written by Tom Kimmel, Jeff Franzel, Mark Luna 
Today I took a walk up the street 
And picked a flower and climbed the hill 
Above the lake 
And secret thoughts were said aloud 
We watched the faces in the clouds 
Until the clouds had blown away 
And were we ever somewhere else 
You know, it's hard to say 
And I never saw blue like that before 
Across the sky 
Around the world 
You've given me all you have and more 
And no one else has ever shown me how 
To see the world the way I see it now 
Oh, I, I never saw blue like that 
I can't believe a month ago 
I was alone, I didn't know you 
I hadn't seen or heard you're name 
And even now, I'm so amazed 
It's like a dream, It's like a rainbow, it's like the rain 
And somethings are the way they are 
And words just can't explain 
Cause I never saw blue like that before 
Across the sky 
Around the world 
You've given me all you have and more 
And no one else has ever shown me how 
To see the world the way I see it now 
Oh, I, I never saw blue like that before 
And it feels like now, 
And it feels always, 
And it feels like coming home 
I never saw blue like that before 
Across the sky 
Around the world 
You've given me all you have and more 
And no one else has ever shown me how 
To see the world the way I see it now 
Oh, I, I never saw blue like that before