HTML5 Update

To get this up to date with HTML5 <time> tags, apply these changes:

line 117:
$result .= $before.'<a href="'.get_year_link($year).'"><time>'.$year.'</time></a> <span>:</span>';

line 137:
$result .= '<a href="'.get_month_link($year,$month).'">'.$time_tag.'</a> ';

line 139:
$result .= $time_tag.' ';

after all that, add this below line 135:
$time_tag = '<time datetime="'.$year.'-'.sprintf("%02d",$month).'">'.$month_abbrev.'</time>';

Optionally, add rel="archives" to the all above lines that have <a> tags.

http://wordpress.org/extend/plugins/compact-archives/