Hello. I made my on board with atmega328p chip. I am using arduino ide and USBasp to write code. However, I can't use serial monitor. Serial monitor was best tool to debug arduino. Is there a way to somehow get output window using usbasp? 
(deleted)
I think it's possible but not terribly easy. I've never seen anyone actually report having used it but there is this:
http://community.atmel.com/projects/usbasp-tty-usbasp-programmer-modified-serial-support-and-terminal-program
It says:
this requires the modification of the USBASP programmer to add the necessary RXD & TXD connections.
as far as I know none come with these connections in place. Typically pins 4&6 on the 10pin connector are
connected to ground but can be made available for these connections with some careful soldering.
My understanding is that some of the cheap 10-pin USBasp programmers you can buy on eBay in fact do have the serial pins already wired to the 10-pin connector. If you have the 6-pin USBasp version you'll need to do some soldering.
If you have any success with this please update as I'm interested.
I think I will use USB-TTL adapter Making SPI from USBasp looks too hard for me