Looking for a breadcrumb menu that can be called (preferably from a sidebar widget in header.php) that lists…
Home > Parent Post/Page > Current Page/Post
or alternately…
Home > Parent Category > Current Page/Post
or even
Home > Grand Parent Category > Parent Category > Current Page/Post
Breadcrumb NavXT will let you do that, it has a built in widget and supports just about everything WordPress can do (breadcrumbs spanning multiple sites in a multi site setup does not work, yet).
Check out Yoast Breadcrumbs. Very well written breadcrumb menu plugin.
I use this
http://dimox.net/wordpress-breadcrumbs-without-a-plugin/
you can call it anywhere you want/need a (clickable) breadcrumb trail