communication via serial interface uart (e.g. by adapter usb → com)
small size, to 512 bytes (this version is prepared for Atmega32, but it can be also any other AVR microcontroller)
flash programming faster than avrdude
fast data control (so you can skip read as it happens in avrdude)
remote reset (by DTR, RTS lines)
integration with WinAVR
Extras:
Flash read
store and read in EEPROM (in terminal mode)
fusebits and lockbits read
Additional advantages:
with previously loaded bootloader you can program even if you block ISP, reset, etc. by fusebits
the code is completely free, licence MIT (X11)
How it works in practice – screenshot of Programmer's Notepad:
After loading the bootloader, you need only a simple interface like adapter com/usb and system max232 – shown in the following picture. You can also use Bluetooth adapter (e.g. BTM-222) or ftdi.