I just saw a list of all the unreleased songs:
1. Outta Control (confirmed)
2. Tell Me What You're Sippin' On (confirmed)
3. Girls and Boys (Linda Perry)
4. Turn On The Night (old song)
5. More Than You Know feat. Timbaland (confirmed)
6. Baby Can't You See (Neptunes)
7. Stay (mentioned by Shep Soloman)
8. Free (Guy Chambers/Cathy Dennis/Britney Spears)
9. Sacred (Guy Chambers/Cathy Dennis/Britney Spears)
10. Hollow (Bloodshy/ Cathy Dennis/ Britney Spears)
11. Wonderland (Harry James/Muhammad Balawa M/Safinia Reza/Soloman Sheppard J/Britney Spears)
12. When I Say So (Brian Kierulf/Joshua Schwartz/Britney Spears/Brian Transeau)
13. Chaotic(Original In The Zone track listing)
14. The Zone(Original In The Zone track listing)
15. So Sensual(Original In The Zone track listing)
16. You Gotta Dance(Original In The Zone track listing)
17. Every End is A New Beginning(Original In The Zone track listing)
18. I Said (Rodney Jerkins/Guy Chambers)
19. With Another Girl(William Orbit)
20. Cuz U're Looking So Good (Feat. Pharrell/Neptunes)
21. Brand New (Rodney Jerkins)
22. The Way I Feel (Babyface)
23. It's Funny Now (William Orbit)
24. I Don't Want You (Neptunes)
25. Nothing (Fred Durst)
26. Funk It Up (Rodney Jerkins)
27. You Thought Wrong (William Orbit)
28. Take Ya Home (Neptunes)
29. Weakness (Dan Kenney)
"All That She Wants" - Blackout Sessions, 2007.
"Already Bad" - Upcoming Album Sessions, 2009.
"Amnesia" - Upcoming Album Sessions, 2ATM" -
Upcoming Album Sessions, 2009
Dramatic" - Blackout Sessions, 2007.
Everybody" - Blackout Sessions, 2007.
"Girls And Boys" - The Original Doll, Unreleased album.
"Guilty" - The Original Doll, Unreleased album.
Luv The Hurt Away" (...Baby One More Time, 1999)
Little Me (Just Yesterday)" (Blackout, 2007)
Love Is A (State Of Grace)" (Blackout, 2007)
"Let Go" (Blackout, 2007)
My Love Was Always There" (Dream Within A Dream Tour, 2002)
"My Only Wish (This Year)" (...Baby One More Time Platinum Christmas, 2000)
My Baby" (Britney's Upcoming Album, 2009)
"Get It (I Said)" - The Original Doll, Unreleased album
Open Arms" (Britney's Upcoming Album, 2009)
Outta This World" (Blackout, 2007)
"One More" (Blackout, 2007)
"Pull It" (Blackout, 2007)
Quicksand" (Britney's Upcoming Album, 2009)
Sugarfall" (Blackout, 2007)
Tell Me What Your Sippin' On" (Feat. AC) (Blackout Sessions, 2007)
"Underground" - Upcoming Album Sessions, 2009.
baby boy-blackout
"Mystic Man" (Dream Within A Dream Tour, 2002)
"Open Arms" (...Baby One More Time Tour, 1999)
"Vogue" / "Material Girl" / "Black Cat" / "Nasty" (Medley) (...Baby One More Time Tour, 1999)
"Weakness" (Dream Within A Dream Tour, 2002)
"You Were My Home" (Dream Within A Dream Tour, 2002)
and a track list for her new album is
"Amnesia" (Sixth Studio Album, 2009) [Confirmed By Fernando Garibay Song-writer]
"Broken Promises" (Working Title, New Music 2009)
"Conscience" (Working Title, New Music 2009)
"Do You Ever Feel" (Working Title, New Music 2009)
"Get It" (Working Title, The Original Doll Album/Axed Album)
"Motherlove" (Working Title, Blackout Sessions, 2007)
"My Baby" (Sixth Studio Album, 2009) [Confirmed By Britney In OK! Magazine 2008 Interview]
"Quicksand" (Sixth Studio Album, 2009) [Confirmed By Lady GaGa]
"Red Carpet" (Working Title, Blackout Sessions, 2007)
"Rebellion" (Working Title, Comeback Demo)
"Stick It Out (In The End)" (Working Title, New Music 2009)
"Underground" (Sixth Studio Album, 2009) [Confirmed by Larry Rudolph & Lady GaGa]
"Voodoo" (Working Title, Blackout Sessions, 2007)
"Womanizer" (Sixth Studio Album, 2009)
(Taken from Britney.com)