I would like to design a web page Gui where users can design a simple interactive garden. The user would pick a template design and receive price estimates based on the design template and the dimensions entered.
I'd like the user to be able to move items such as plants, stones and be able to adjust the dimensions of the grass, paving.
I'm thinking i could make it using flash but I would like to know there are any other ways I could use to implement this?
You probably can get this to work using basic jQuery, CSS, and HTML.
It sounds like maybe you don't have a detailed design yet of your UI. HTML, AJAX, Flash, and Silverlight all suck as design tools - you should start out with detailed wireframes, flow charts. Start with pencil and paper and work up to Illustrator or maybe SketchFlow if you must.
THEN the technology can be chosen based on the requirements. You can accomplish a lot in each technology mentioned, as long as you have good discipline.