How to add modules to aspx page

Hi
I'm looking for a right way adding different modules into my cms. For example:
The user will have an ability to add some modules like contact form, text editor and etc... But in different places of a webpage.
I thought about panels using, I need to place them beforehand in my wanted places of a webpage and I think that will be ok,
but I don't know how to let a user a possibility to change the panels between them, something like Igoogle, maybe without ajax.
and also to give a possibility to align the panels right, left or middle of the page. 

Thanks 
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