pathartl

Accordion Archive Widget is exactly what the name implies. It recreates the stock archive widget, but this time around the widget is laid out as an accordion. It gives you the years of the archive, and then when the year is clicked it expands to show the months.
Development can be tracked at http://github.com/pathartl/accordion-archive-widget

Accordion Archive Widget

An archive widget that reconstructs the stock widget into an accordion by year with month children.

CPK Web Solutions

Use this widget to filter your archives. For example if you’d only like archives for posts in category 2, simply enter ‘cat=2’ into the widget settings form. The widget allows very complex filtering rules. You can even alter the number of posts displayed on an archive page.

CPK Ultimate Archives

An improved version of the default WP Archives widget that allows complex filtering.

Accordion Archive Widget vs CPK Ultimate Archives