Alright, now that the OP glitch is fixed, I finally updated this! This is what got released since April 2nd:
The Allman Brothers Band - Southbound
Sweet - Ballroom Blitz
Creedence Clearwater Revival - Have You Ever Seen The Rain?
Rise Against - The Good Left Undone
The Vines - Get Free
Modest Mouse - Float On
And of course, all of these are in Rock Band except for Southbound.