This post on the SEOmoz blog will give you special focus on SEO related WordPress issues using Yoast’s SEO for WordPress Plugin. This is a must read if you’re using WordPress and want the SEO basics covered.
Responsive web design is on the rise and so is responsive images and videos. FitVids.js is a lightweight, easy-to-use jQuery plugin for fluid width video embeds. Chris Coyer from CSS-Tricks did a screencast on how to integrate this into your WordPress installation. I recently did the same thing and posted a comment on Chris’ article, so I won’t go into more details.
As of WordPress Version 2.3 the wp_tag_cloud() function is available to developers which will display a list of tags, where the size of each tag is determined by how many times that particular tag has been assigned. The default title text for tag cloud links has the following format '%s topic', '%s topics' (where %s is the number of times the tag has been assigned). The function parameter topic_count_text_callback will allow you to override the default title tag function in WordPress.
The in-depth guide on using Ajax with WordPress by Ronald Huereca is now available as a free download as PDF.