I've had a couple people private message me on how I got the sidebar nav to work with ecwid... Very simple to do in wordpress using the custom menus option combined with the custom sidebars plugin:http://wordpress.org/extend/plugins/custom-sidebars/
All you have to do is create a custom sidebar, then apply the custom menu to that sidebar the store will placed.
When you set up your custom menu in wordpress just link directly to the product or category you'd like. If in doubt just browse your store and copy the link directly from the browser address bar.
The shopping bag widget is in the top sidebar position, the store menu in the second widget position.