I am looking for a program that can integrate applications into a Windows 7 SP1 x64 Ultimate installation ISO. Just like nLite can do with Windows XP (using pre-existing nLite Addons or creating new ones). Free is better.
You can give RT Se7en Lite a try. Personally I have used this to aid with the installation of a new computer for my Dad, since it can take a lot of time to reinstall everything and you can miss certain programs.
RT Se7en Lite is developed by Rockers Team to customize windows 7 operating system and to make it lite. You can add wallpapers, Icons, themes, integrate updates, drivers, language packs, applications, remove components, enable or disable features, unattended installation settings, bootable ISO and USB creator , etc. It will be very easy to operate and changing the style of your windows 7 operating system.
Its important to note that this only works with Windows 7 Desktop and not with Windows Vista or 8.
Here is a Life hacker tutorial on how to use it if you wish.
Making the image