If you are looking to work with Grid Based Web Design, here is a link with a lot of choices for you to try out.
Dreamweaver currently uses the Golden Grid System in its Responsive Design Boilerplate.
My actual favorite “du jour” , but not listed here, is Gridulator.com.
There’s a new online wireframing app called wireframe.cc. It’s a bare bones wireframing app that allows you to create a website wireframe ad hoc and actually saves it to the internet with an address for you to refer back to. Interesting tool if you wanna throw an idea at someone quickly.