I needed to do this post for myself own good. While content of the Wordpress.org documentation wiki
sure is invaluable to me as a plugin developer - I get so frustrated by the organisation and
structure - or should I say lack of the same.

I spend some time each morning trying to find (through search of course) the pages I “always”
need.

So here are some quick links:

http://codex.wordpress.org/Conditional_Tags
defines use of functions such as
is_home
is_admin
is_single
is_page()
is_category()
in_category(’5′)
is_author()
is_date()
is_search()
http://codex.wordpress.org/Plugin_API
startpage for plugin developer, noting of value but for beginner
http://codex.wordpress.org/Plugin_API/Action_Reference
action hook reference
http://codex.wordpress.org/Plugin_API/Filter_Reference
filter hook reference

Other hook and filter lists

http://blog.taragana.com/index.php/archive/wordpress-2x-hooks-for-action-comprehensive-list-for-plugin-and-theme-developers/

http://blog.taragana.com/index.php/archive/wordpress-2x-filters-comprehensive-list-for-plugin-and-theme-developers/