This plugin will wrap multiple html <p> tags around selected lines of text as long as there is at least one blank line separating the lines.

It will turn this:

line of text
line of text

line of text
line of text

Into this:

<p>line of text
line of text</p>

<p>line of text
line of text</p>

This plugin can be downloaded from this page on the HTML-Kit web site. Installation instructions, etc. are also provided.