I was unable to find a custom html widget with Joomla style assignment. Like you create a module (widget), define some HTML and assign it to certain menu items (or set it to show everywhere except the selected etc). Given WordPress doesn’t have the same menu system, the widget has to be able to assign itself to certain pages, post categories and tags.
Hardcoding conditional tags into the template won’t work…
Thanks for your help.
edited: I have come across this plugin. The problem is I need something easy to use for untechy guys. Like a set of checkboxes containing names of pages and categories.
This plugin might help you : Widget logic
EDIT
There are also many variants of this kind of plugin listed in this article. Maybe you’ll find one that suits your needs there.
I am not sure I understand your specific “Joomla-style” needs, but in WP conditional display of widgets is commonly implemented by using plugins that extend native widget controls.
For example Widget Logic.
This is what you need, lets you assign a widget to a specific page, just like joomla modules
http://www.woothemes.com/woosidebars/