Oddthinking

If your blog is over a year or two old, you may have noticed the list of archive pages is getting unwieldy.
This plugin is a widget that compresses the size of the arcgives list to two lines per year (three if the lines are narrow) rather than one line per per month.
<h3>More information</h3>
This widget is licensed under <a href="http://www.gnu.org/licenses/gpl-3.0.html" rel="nofollow ugc">GPLv3</a>.
Grateful thanks to <a href="http://tech.windsofstorm.net" rel="nofollow ugc">Alan Morgan</a> whose widget_archives2 I used as a template.
Potential developers should check out the <a href="http://www.somethinkodd.com/oddthinking/2007/03/29/more-theme-changes-2/" rel="nofollow ugc">development history</a>.
Finally, an obligatory plug for my blog, <a href="http://somethinkodd.com/oddthinking" rel="nofollow ugc">OddThinking</a>.

Compact Monthly Archive

Show a monthly archive list in a compact format - one letter per month.

robfelty

Create collapsible archives by year or month. Features include: link to archive pages, display of individual posts and support for custom post-types.
<h3>Demo</h3>
I use this plugin in my blog at http://blog.robfelty.com

Collapsing Archives

Very helpfull

This plugin uses Javascript to dynamically expand or collapse the set of months for each year and posts for each month in the archive listing of your  …

Compact Monthly Archive vs Collapsing Archives