chapter 1

The first step in the development of any micrcontroller is to know about its architecture and instruction set. So i advice you all to keep a copy of instruction set and architecture manual. You can download them from the link below.
AVR Instruction Set
Architecture Manual or Datasheet for your AVR Microcontroller

The above document will help you to get familiar with the instruction set and to know about your AVR in a better way.
After this, we now have to decide the IDE on which you are going to work or write program for your AVR. I advice you to use AVR Studio 4 from Atmel Corporation, which is a free IDE for AVR and it has many features like programming, debugging etc.
You can get your free copy of AVR studio from link below.
AVR Studio 4.12 (build 460) (45 MB, updated 11/05) - Registration needed
AVR Studio 4.12 Service Pack 4 (build 498) (25 MB, updated 10/06) - No registration
AVR Studio 4.13 (build 528) (73 MB, updated 03/07) - Registration needed

So you can download any of the copy above as per your need more information about AVR studio can be obtained from
AVR Studio 4

All documents and IDE for writing program is ready.. only thing left is a programmer, with which we are going to program our AVR. As we know almost all AVR comes with ISP (In System Programmable) ports. So you don't need any special hardware to program your AVR. Please see the link below for ISP programmer for AVR.
Download PonyProg - serial device programmer

Note: Do not forget to run the setup after installing PonyProg.

Setup Information:
In interface setup, select parallel and then from the drop down select AVR ISP I/O.
slect the LPT Port (parallel port) available on your PC. Then click ok!

To load Hex file:
Go to File-> Open Program (FLASH) file
then from the drop down where ".e2p" is show, select ".hex" and load your hex file.