I have developed a new wordpress plugin that is free for anyone to use called LJ Multi Column Archive. I have been looking around at other blogs recently and seen a fair few that had archive lists that where huge, after a couple of years the list can take up most of your sidebar space.
So I decided to write a plugin that would put your archives list into columns, unfortunately it only solves the problem for a short while but I think at the moment I will be happy using this plugin until i have at least 24 months worth of content (and that is a while away yet). When that time comes hopefully there is something better, or I will just have to develop something else.
Check it out in the WordPress Extend site.