Creating Dropdown Filter Search of Taxonomy Terms (similar to www.lynda.com.au homepage)

Hello

I want to create a similar search functionality to that available on http://www.lynda.com website [for searching courses]

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What I have already configured:

I have a defined vocabulary, which has about 10 Terms (main categories) and each of those 10 terms has 8-10 child terms as well (sub categories). Many of these child terms - at times have sub-categories too.

When a user wants to create a new story, in the content creation page, I have put in a "required" option to select the deepest taxonomy term [achieved using hierarchical select option widget]. This ensure that all nodes are strictly associated with the deepest level taxonomy term.

Using path auto (url alias), I have structured my url in such as way as to display the following path:

www.mysite.com/categoryname/sub-cateogryname/[title-raw].

The site is so designed that many nodes (acticles/ stories/ etc) can be attached to the deepest level taxonomy term.

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What I want to achieve is:

1. A block which has two drop down boxes. From the first box - the user selects 1/10 terms (main categories), the sub-categories then get dynamically updated and in the second box - the user selects the 1/10 related sub category and hits submit (ignoring further sub categories). On enter, a list of all nodes which match these criteria should be displayed.

2. I want a [block in grid format] on the main page (4 x4) grids or mini blocks. Each grid would have an image (for the Category) and the Main category (parent term) - linked to node and then below it a list of top 3 sub-categories (linked to node) and a more... button.

For a graphic explanation - You can look at Lynda.com. On the home page they have these filtered search for courses. This is what I need for requirement 1.

I have been trying various approaches and have not got the desired result. A way out was to create a menu for taxonomy.. which I have already done, but this is not what I want to achieve.

Would someone be able to help me out with this ??

Cheers
Anand