It would be nice to know which Os you are using. Personally I use an app named Papparazzi! on Mac OS X

This website is pretty cool for responsive screenshots http://placeit.breezi.com

You can choose to grab screenshot by URL and it places it for you.

@sorrentandrea, I use the chrome plugin for fullpage screen shots, but I think Adobe's Edge Inspect also has a screenshot tool, but I've never used that part of Edge Inspect.

@sorrentandrea, it's called Webpage Screenshot, it's very basic, but gets the job done..

http://www.webpagescreenshot.info

@treeRoot I'm able to do the job without any program, I was asking for something automatic, but it don't seem to exist. =)

@ChrisP thanks I'll give it a try =)

I've been experimenting with phantomjs. If you take the example rasterize.js file and alter it ever-so-slightly so that you can plug in values for width/height, you can get a screenshot in a split second.

Furthermore, if you have a basic understanding of JS, it should super easy to make a script that will hit the site you specify, and take a series of screens at specified resolutions and spit them out into a folder for you, named appropriately.

Many thanks to Melindrea for mentioning phantomjs in another topic -- it's awesome.

Here's a (very) basic script to take a screenshot with a set viewport width:

var page = require('webpage').create(),
    system = require('system'),
    address, output, size;

if (system.args.length < 3 || system.args.length > 5) {
    console.log('Usage: rasterize.js URL filename [viewport width] [zoom]');
    console.log('  Viewport Width: "800"');
    phantom.exit(1);
} else {
    address = system.args[1];
    output = system.args[2];
    pxWidth = system.args[3];
    page.viewportSize = { width: pxWidth, height: 600 };
    if (system.args.length > 4) {
        page.zoomFactor = system.args[4];
    }
    page.open(address, function (status) {
        if (status !== 'success') {
            console.log('Unable to load the address!');
            phantom.exit();
        } else {
            window.setTimeout(function () {
                page.render(output);
                phantom.exit();
            }, 200);
        }
    });
}

Usage: phantomjs path/to/screenshot.js http://example.com example.png 1024

Or you could alias it in your .bashrc like I do: alias screenshotjs="phantomjs ~/Development/phantomjs/examples/screenshot.js" and call it like: screenshotjs http://example.com example.png 1024

You could just as easily set up a script to take several shots at predefined viewport widths, too, like in this post: http://jonathanmh.com/automate-mobile-testing-phantom-js/