GRUB - Multiboot boot loader
Grub2Win - Safely dual boot Windows and Linux without touching the Windows MBR.
coreboot - coreboot is an extended firmware platform that delivers a lightning fast and secure boot experience...
PLoP Boot Manager - The PLoP Boot Manager is a small program to boot different operating systems.
U-Boot - Das U-Boot (the Universal Bootloader) and Embedded Linux
EasyBCD - EasyBCD is NeoSmart Technologies multiple award-winning answer to tweaking Windows bootloader.