Odd archive listing

I was wondering if someone knew of a plugin, or had a general idea for how I could do an odd way of listing archives. I’m not asking for specific code, but just a general point in the right direction, because I’m a little stumped on this one.

My archives list is getting HUGE – kinda overwhelming the page. I could relegate it to it’s own page, but I like it in my sidebar. So I was wondering if there were a plugin (or a method) to basically list the most recent 6 months as a regular unordered list, but then have anything older than that show up in a dropdown, to kind of conserve real estate.

I’m thinking it can be done, and I have the beginnings of an idea on how to do it, but I figured rather than do “trial and error” I’d see if it’s been done yet and if someone can point me to it.

Thanks!