Easel is designed to help you quickly design high-fidelity mockups.
Pro Quickly creates high-fidelity designs
If you want something a little more high-fidelity than the usual mockup tools, yet still want to rapidly prototype your design Easel is perfect.
Easel is designed to generate pixel-perfect designs utilizing both template libraries, drop and drag and CSS3. Easel lets you skip the HTML and get right to the design.
Pro Perfect for designing Bootstrap sites
Pro Awesome at doing re-designs
It really shines when it comes to re-designs of existing websites. A chrome extension grabs elements from your site and you can then easily paste it into a Easel doc and drop and drag it around.
Con Service is shutting down
Great service, sadly no longer with us.