I have a 2 level navigation. On the top I'm listing only the parent categories and what I want to accomplish is when I click on a particular post I want to have a sidebar where it lists the child categories for the particular parent category.
For more clear presentation, here is a sample menu
Now, suppose I have a post under Technology. When clicked single.php is shown and I want to show a sidebar with the child categories (Gadgets, Microsoft, Hardware) from the active parent category.
A bonus would be if this can be accomplishable even if I have a post filed under a child category (Gadgets for example) and still list the sibling categories.