Currently the mega menu is often used to replace menus with a lot of dropdown levels.
They are an excellent design choice for accommodating a large number
of options or for revealing lower-level site pages at a glance.
Mega Menus Beat Regular Dropdowns
We know from user testing that mega menus work. Here are some arguments to support this empirical fact:
- For bigger sites with many features, regular dropdown menus typically hide most of the user's options. Yes, you can scroll, but (a) it's a pain, and (b) scrolling hides the options at the top of the menu. As a result, you can't visually compare all your choices; you have to rely on short-term memory. People have enough on their minds, and messing with short-term memory reduces their ability to accomplish tasks on your site. Mega menus show everything at a glance, so users can see rather than try to remember.
- Regular dropdowns don't support grouping unless you use kludges, such as prefixing secondary choices with a space character to indent them. Mega menus let you visually emphasize relationships among items. This again helps users understand their choices.
- While plain text can be wonderful, illustrations can indeed be worth a mouthful of words, as the Moleskine example shows. Mega menus make it easy to use pictures and icons when appropriate. And, even if you stick to text alone, you have richer typography at your disposal (letting you differentiate link sizes according to their importance, for example).
You can find examples here