So, I've been playing around with Adobe Muse. It is a web design and layout tool created by Adobe. It is included in their Creative Cloud membership. It is A-M-A-Z-I-N-G! It allows you to intuitively lay out an entire website from Planning to Design to Preview to Publish. All in one application.
The layout tools are similar to InDesign's page layout tools. You can make content boxes and text boxes, resize them and make them responsive. The tool has been around for about four years now. I am just learning it now and playing around with it and I have to say, "Where have you been all my life?"
It really is much easier than Photoshop mock-ups, you don't have to hand code anymore. Although, I think if you wanted to add more complex features and styling, you'd have to go into the code and tweak it quite a bit. But what is nice is you can quickly build the basic structure of your site, add graphics and icons, navigation, and even widgets such as slideshows and contact forms with basic functionality, without coding a thing.
In the coming days, I'm going to do a quick screencast to demonstrate how to build a simple one-page scrolling website with fixed navigation at the top. It literally took me around 15 minutes to complete the basic structure of the site, preview and upload it to my FTP host. AMAZING!