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.

thedonjenkins

A plugin that add a sidebar widget to presents a list of posts from the same day/week/month last year.
Last year post widget has the ability to bring back posts from the past. Using the blog chronology constantly pushes great content into the archives. This sidebar widget, Last Year, brings posts from this day, week or month last year back!

Last Year Post Widget

A plugin that add a sidebar widget to presents a list of posts from the same day/week/month last year.

Accordion Archive Widget vs Last Year Post Widget