Gentoo glibc sources:
http://dev.gentoo.org/~vapier/dist/
Gentoo glibc CVS interface:
http://sources.gentoo.org/viewcvs.py/gentoo-x86/sys-libs/glibc/files/digest-glibc-2.5?rev=1.6&view=log
Find the latest releases:
http://gentoo-portage.com/sys-libs/glibc

Discussion of LD_ASSUME_KERNEL and tls
http://people.redhat.com/drepper/assumekernel.html

Useful for checking their builds:
http://buildd.debian.org/build.cgi?arch=arm&pkg=glibc

http://www.linuxfromscratch.org/lfs/view/development/chapter05/glibc.html

LFS:
http://cross-lfs.org/view/clfs-sysroot/arm/cross-tools/glibc-headers.html