How to limit WordPress search to certain categories
This is a great tip for limiting the built in search functionality to search only the category you specify. The author provides the code for searching just a single category or searching only the children of a certain category.
Edit your WordPress database using SQL queries
I don't know about you, but I've always been a little afraid to run queries directly on my WordPress database. This post goes through how to accomplish many tasks using queries. Sometimes the task of going post by post to make a change would take you 10 times as long...
Show ads only to search engine visitors
Search engine traffic is where you really make money on Adsense, so some blog owners choose to show ads only to visitors who come in through the search engines. This article explains how to accomplish that and to show alternate content to other visitors.