
This plugin by Shivendu Madhava is one of my favorites. Small, simple and adds stylish look to your posts/pages. It is so simple that my review consists of examples only!
Examples:
This is a note
<p class="note">This is a note</p>
This is an alert
<p class="alert">This is an alert</p>
This is a help box
<p class="help">This is a help box</p>
This is important
<p class="important">This is important</p>
This is a tip
<p class="tip">This is a tip</p>
This is linux
<p class="linux">This is linux</p>
This is windows
<p class="windows">This is windows</p>
Very simple. Isn't it?