If you find yourself with a Terminal window open:

     alias win7="bless -mount /Volumes/win7/ -legacy -setBoot -nextonly; shutdown -r now"
     alias debian="bless -mount /Volumes/wheezy/ -legacy -setBoot -nextonly; shutdown -r now"
     alias arch="bless -mount /Volumes/arch/ -legacy -setBoot -nextonly; shutdown -r now"

Obviously change the volume paths as needed. Typing "win7" into terminal will restart into my Windows 7 install, likewise for "debian" and "arch". Any subsequent reboot will automatically reboot back into OSX