This article lists 10 Useful WordPress Hacks & WordPress Functions that you will find helpful when developing your own wordpress themes. A few of my personal favorite WordPress Tips in this list are Caching custom WordPress queries and Deluxe Blog Tips Meta box script for easy custom metabox creation.
1.) How to Remove the Width & Height Attributes From WP Image Uploader
When creating a responsive WordPress theme you may need to remove the default image height and width attributes that are automatically added by the WordPress media uploader.