Always trying to improve my WordPress skills and learn actions and filters. This guys make it easier FOTD. Each day I get three emails, each email contains a new WordPress Filter. Each filter is explained as well as the filter has a use case. As the author states, not all use case examples are awesome, but the goal is to get many of the examples to use in the Codex/Code Reference.
So subscribe to his email list and within one year you will be introduces to over a thousand filters available in WordPress right from your inbox. Get on the mailing list soon as he is only on #9 of the 1003 he plans on exploring. Thanks.