OSDev.org

Hi,
I just set up a VFS en initrd using GRUB and I also set up syscalls and I even setup multitasking. Now I was wondering would it be hard to place a "*.bin" in my VFS and execute it?
And where in the *.bin-files does the actual code starts?

It starts wherever you want it to. You have control over paging, so you have control over where your programs run. If you're not using paging (bad), just find a good spot in physical memory to put it.
If you want a simple executable, write some PIC and assemble it as a flat binary file. Then put that in your initramd and run it anywhere.