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.

tysonlt

Helps Shopp integrate with caching plugins. Currently designed for W3 Total Cache, but the cookie strategy will work for any cache plugin that monitors cookies. 
Other caching plugins will require manual configuration, but W3 Total Cache is configured automatically. * Automatically integrates with W3 Total Cache to configure caching settings – no other configuration is required! * Automatically configures common Shopp paths that should not be cached (W3 Total Cache only) * Sets a cookie whenever the cart is updated. If the cart becomes empty the cookie is purged. 
* Sets DONOTCACHEPAGE constant on ‘init’ action to make sure that pages with shopping cart items are never cached. * Clears the cache when product, category etc. details are changed.

Shopp Cache Helper

Helps Shopp integrate with caching plugins. Designed for W3 Total Cache, but will work on any cache plugin that checks for custom cookies.

Shopp Custom Categories Widget vs Shopp Cache Helper