How to change MAC address permanently for Ubuntu 9.04
 

I need to change MAC adress permanently, but without loosing networkAppet.
It should be as early as could.

The first question I would ask is why would you need to do such a thing? As for 'permanently' your new MAC address would need to be re-set with every reboot, so inclusion within a startup script would be highly recommended.

I need to do that because ISP assign service by MAC. I have 3 laptops and i can't connect them without changing MAC. Could you please show such script?

create your own interface and assign the MAC to this interface, the do:
Alternatively you can put the fisrtline into a startup script, so that the current mac can be changed everytime you reboot without creating a new interface.

Where exactly put script? /etc/init.d ?
create such file?
#!/bin/sh
ifconfig eth1 down hw ether 00:18:f3:3a:2e:dd
ifconfig eth1 up

something like /etc/rc.d/rc.local