Install without Disks

Nope.

If you mean a downloadable version of the full installer for either Leopard or Snow Leopard, no, there is not and will never be one available since the Mac OS X installer must be able to boot from the disk to install.

You have some options:

1) If you have an external hard drive and a friend with a Mac, buy the retail Leopard or Snow Leopard disk, connect your hard drive to your friend's Mac and use Disk Utility to restore the Leopard/Snow Leopard disk to the external hard drive. You can then boot your MacBook from the external drive and install that way.

2) If your MacBook has Firewire, you can put it into Target Disk Mode and connect it to another Mac from which you can install Leopard/Snow Leopard on the MacBook. I don't recommend this method since it's not always reliable (the installer will attempt to install drivers based on the hardware in the Mac you're using and so you may not get the correct drivers for the MacBook), but people have found that it works for them.

3) Buy an external USB DVD drive. Many people have had success booting the Mac OS X installer DVD in external drives.

If your MacBook has Firewire, the Firewire DVD drives tend to be more compatible with booting Mac OS X isntallers. Albeit there are USB DVD drives that are compatible.