Barry Hughes

This plugin works with and depends upon the Shopp e-commerce plugin for WordPress. It is designed to integrate with the 1.2.x branch of Shopp and has been successfully tested with Shopp 1.2.1.
Enough of that, what does it do?
<ul>
<li>Shopp already ships with a widget that can be used to display product categories. This is an alternative to that widget.</li>
<li>Select only those categories that you wish to include, ignore the rest.</li>
<li>Easy to use: simply check the boxes for the relevant categories, choose the display mode (dropdown, regular list etc) and you’re done.</li>
<li>A convenient way to build category-based store menus in the sidebar!</li>
</ul>
This plugin was written by <a href="http://freshlybakedwebsites.net" rel="nofollow ugc">Barry Hughes</a> and can be supported by <a href="http://freshlybakedwebsites.net/say-thanks-with-a-beer/" rel="nofollow ugc">buying the author a beer</a>.

Shopp Custom Categories Widget

Provides an alternative category widget featuring fine grained control for use with the Shopp plugin.

Shoppdeveloper.com

By default the Shopp breadcrumb will display “the path you followed to get here”. And frankly, that is 
what breadcrumbs are meant to do. However this means when someone enters one of your product pages using 
a direct link, the breadcrumb will be empty. It will just show the link back to the main Shopp page. 
With this plugin installed you can use breadcrumbs that show “where you are” in the hierarchical 
structure of categories.

Shopp Default Breadcrumb Extender

Add hierachical breadcrumb to your Shopp webshop product pages.

Shopp Custom Categories Widget vs Shopp Default Breadcrumb Extender