Your latest useful link.

Okay, forget the long link and site-walk the menus.

ATMEL
http://www.atmel.com/

and then navigate Home->Design Support->Search->
Application Notes or User Guides

They cover a lot of how-to. Not what I was I was looking for but tons of interesting subjects.

rofl
If you click on the link it states "no pages found"
This should work (I hope) http://www.atmel.com/search.aspx?filter=0&btnG=Search&site=en_collection&client=support_frontend&proxystylesheet=support_frontend&output=xml_no_dtd&getfields=*&oe=UTF-8&ie=UTF-8&ud=1&exclude_apps=1&num=1000&access=p&sort=date:D:L:d1&entqr=3&entqrm=0&lr=lang_en&q=inmeta:asset_type~User+Guides&dnavs=inmeta:asset_type~User+Guides

Maybe an idea to shorten the links with

or similar services?

the long one above becomes e.g. - http://goo.gl/PZ0Gh -

I hope most people don't like a shortened URL. I like to see what site I am going to. 99% of the time I will not go to a tinyurl (or other shortening links) because I do not know where it leads.

Rearranged the OP. Source site is www.atmel.com.
Menu Design Support->Application Notes to start then enter a chip name in search to narrow the list, or just AVR.

And today I'm trying to figure out why I can't find what I was reading last night...

I think I saved one pdf on integer math techniques. Saw on on BCD but didn't grab it.
Always finding 100 things I wasn't looking for while searching for something else.

My favorite Atmel starting point
http://www.atmel.com/products/microcontrollers/avr/megaAVR.aspx

(Thanks to westfw) The "Atmel AVR Toolchain", available for windows and linux, is now using avr-gcc 4.7.2 :
http://www.atmel.com/tools/ATMELAVRTOOLCHAINFORWINDOWS.aspx

For fresh meat...
A great place to start... Arduino Tutorial - Learn electronics and microcontrollers using Arduino!
More of an overview than a tutorial but also good... http://arduino.cc/en/Tutorial/HomePage
This looks promising... Adafruit Learning System