If you're auditoning for college, avoid using anything that's currently on Broadway, or that has recently been on Broadway (i.e. Thoroughly Modern Millie, etc), unless it's a revival. And for the love of god, don't sing anything from Wicked. I've been to the Unified auditons in Chicago and NYC for the past 2 years and if I hear anyone else belt Defying Gravity (badly) I'm going to shove pointy things into my ears.
On a more positive note, a few good, solid alto songs are: As Long As He Needs Me from Oliver, The Sweetest Sounds from No Strings, The Real Love of My Life from Brigadoon, anything from Annie Get Your Gun, or if you're looking for something a bit more current, try You Can Always Count on Me from City of Angels.
I can't talk now. I gotta go get my wallet out of the toaster.
Gypsied, I'd respectfully disagree with you on some of those choices, particularly "As Long As He Needs Me" and "You Can Always Count On Me." Those songs are overdone and they are both very negative. Chevstriss said it well - they both discuss bad personality traits and don't make you look good. Pick more positive stuff.