Hey guys, Im not sure abouth one thing. Arduino uno need atmega328 with bootloader. It won't work with normal atmega328. Does ATmega1280 has any bootloader or i can use every ATmega1280. I'm telling because i was thinking about build my own arduino mega :) Thanks.

The 1280 needs a bootloader as well.

Bootloaders are not difficult to burn into bare chips. An ISP programmer ($10-$30) or another Arduino will do it.

Any chip you use will need a bootloader to work with the ArduinoIDE. You can use your Arduino as an ISP (in system programmer) to “Burn” or program the bootloader to your chip. You can buy 328P chips from a number of sources with the bootloader already on them, or you can save a dollar and buy the blank chips. Research Arduino as ISP and you will find info on how to connect things and some instructions on the correct process.

thanks guys, i want to burn the bootloader with arduino as isp but how to connect it to ATmega1280?

Connect the same way as any other chip. Connect crystal & caps, reset pullup resistor to the '1280. Connect the SCK, MISO, MOSI, +5V, GND and control of the Reset lines between chips. Program.