Update September 2008: With WordPress 2.6 +, image captions are built into the core image/media manager so no more need for plugins! Also, the video directly below is using WP 2.6.1 and the new media manager, its upload, editing, alignment, and caption function — all built into the core now. See this post that has a new screencast.
Older version of WordPress help video tutorial using an image caption plugin below.
Captions for images are tricky enough, then add text alignment (wrapping) and CSS and it’s a recipe for disaster. Using the “Image Caption” plugin for WordPress and the simple alignment tool in WordPress, I’ll walk through aligning images, their captions, and the surrounding text.