Popup Link Extension
Marja Ribbers has written a very useful Dreamweaver extension, and it's free. The behavior is called Popup Link, and it opens the current link ('a href=www.yourlink.com') in a new window. Here are some of the features:
No more 'null' links needed -
There's no longer a need to use 'null' links and, as opposed to using 'null
links',
the right click option is still available for the originating link,
and
search engine spiders don't have problems following these links.
XHTML Strict mode compatible -
The behavior resembles using the right click on a link and choosing
'Open in new window'. It also resembles using target="_blank", but the use of 'target'
is not valid anymore in XHTML Strict mode.
Links still work with JavaScript disabled -
The original link is still functional when JavaScript is disabled in the
browser.
You can specify the appearance of popup window - Much
like DW's standard behavior 'Open Browser Window' you can also specify the
properties
of the popup window, including its name, size, and attributes
(whether it is resizable, has a menu bar, and so on).
Does not require a target URL - By default it
takes the current link as the target URL.
You can specify the popup's location on screen.
Here's a screen capture of the UI, shown 75% of actual size:

Here's a link to Marja's site where you can download the free extension (I applied the behavior to the link):
http://www.flevooware.nl/dreamweaver/