Wow! Those apps are really impressive!
I'm not sure what aspect of these online applications do you want to emulate or learn how to program. Cloud-based is not necessary.
Supposing you want to emulate the graphics/drag-n-drop features there are 2 equally valid approaches:
1. Flash / Silverlight / JavaFX
2. Web 2.0 development to the max
Both have pros and cons.
In regards to Flash / Silverlight / JavaFX, the companies that developed them are Adobe-Macromedia , Microsoft and Sun Microsystems (absorbed by Oracle).
These are not really web development, they are programs that are downloaded when you browse for the page. The program is interpreted by a plugin in your web browser (Flash plugin, Silverlight PlugIn or JavaFX plugin). The program is shown on the browser thanks to an object HTML tag...
<object ...=""></object>
All 3 require you to study a language and class library to develop the vector graphics, animation as well as interaction between elements.
Nonetheless, in theory, plugin programs (the aforementioned) are being replaced by Web 2.0 development. Web 2.0 does not refer to an all-new platform but a trend on how AJAX, Javascript and HTML5 are being used. Javascript (not to be confused with Java) and HTML (HTML5 in particular) are platform-indepent, as you may already know. No need for plugins; any recent version of most web browsers can perfectly run any development.
with extensive use of these tools you can drag-n-drop, highlight on mouse over, program events, etc. You may also need some good backend such as PHP or ASP.Net.
However javascript alone, from scratch, would be too much work to achieve something in a reasonable amount of time. A solution to that are javascript libraries (most of them for free) where someone else already worked out the brain-wreaking programming so you can just call a method to do something amazing.
Extract from Wikipedia:
The client-side (web browser) technologies used in Web 2.0 development include Ajax and JavaScript frameworks such as YUI Library, Dojo Toolkit, MooTools, jQuery,Extjs and Prototype JavaScript Framework. Ajax programming uses JavaScript to upload and download new data from the web server without undergoing a full page reload.
My favorite javascript library to do amazing things is scriptaculous (http://www.script.aculo.us), take a look at that and you'll see pretty amazing things with just javascript and no plugin development.
There is no difficult in using a javascript library: You just download it to your PC, put it in a folder related to your web development, include the next tag in your HTML:
<script type="text/javascript" language="Javascript" src="path of your library file .js">
</script>
...And you'll be on your way!
Further reading:
http://en.wikipedia.org/wiki/Web_2.0[
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http://en.wikipedia.org/wiki/Rich_Internet_Application[
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http://en.wikipedia.org/wiki/Adobe_Flash[
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http://en.wikipedia.org/wiki/Silverlight[
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http://en.wikipedia.org/wiki/Javafx[
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http://script.aculo.us/[
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https://jquery.org/[
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