azurecurve

featured-image shortcode allows a floating featured image to be placed at the top of a post. Default settings can be entered to simplify the use of the plugin.
When used several parameters are available for use: 
1. image – to use an image other than the default 
2. title – set a title on the image (will appear in the tooltip) 
3. alt – enter the alt text for when the image cannot be displayed 
4. taxonomy – enter a category or tag name or slug to have a hyperlink added to the image 
5. is_tag – set to 1 for when the taxonomy should be a tag instead of a category
This plugin is multi-site compatible.
This plugin supports language translations. If you want to translate this plugin please sent the .po and .mo files to wordpress.translations@azurecurve.co.uk for inclusion in the next version (full credit will be given). The .pot fie is in the languages folder of the plugin and can also be downloaded from the plugin page on http://development.azurecurve.co.uk.
Current translations: 
Serbian (sr_RS) translation by Borisa Djuraskovic of <a href="http://www.webhostinghub.com/" rel="nofollow ugc">Web Hosting Hub</a>

azurecurve Floating Featured Image

Shortcode allowing a floating featured image to be placed at the top of a post; this plugin is multi-site compatible.

One Crayon

Markup to Featured Image will automatically generate a featured image when you publish a post, with the intent of allowing you to publish posts with featured images from third-party clients like MarsEdit.
To add a featured image to your post, include one of the following markup variants in your post’s content:
<pre><code><img src="/path/to/image.jpg" data-featured-image="keep" />
<img src="/path/to/image.jpg" data-featured-image="strip" />

</code></pre>
If you use an <code><img></code> element, the values of the <code>data-featured-image</code> attribute specify whether the image should be displayed when the post is shown on your site (<code>keep</code>) or ignored when the post is displayed (<code>strip</code>). The order of attributes in your <code><img></code> tag (and whether you include other attributes, like width/height, title, alt, etc.) doesn’t matter. You can make it as complicated or simple as you like.
If the post already has a featured image, the plugin will do nothing (version 1.0 does not allow updating the thumbnail by updating the markup).

Markup to Featured Image

Automatically set the featured image (formerly the post thumbnail) for a post based on custom markup in the body text.

azurecurve Floating Featured Image vs Markup to Featured Image