I have made a new bootloader for ATMega32 which I am using for teaching a course in microprocessor technology. It is based on the code published by Peter Dannegger in 2003 with various modifications. It sends the hex file and possibly eep file from a Windows PC to an AVR prototype board through an RS232 cable or USB cable.
I am posting it here including source code in case somebody wants to use it.
I am using the Olimex prototype board (http://www.olimex.com/dev/avr-p40-usb-8535.html) but you may use any other prototype board. Modifications may be needed if the clock frequency is not 10 MHz.