This Navigation Toolbar (this links to the FAQ) appears as a strip across the top of your computer screen when you're on LJ. It includes a drop-down menu that has a default Journals, Communities, and Syndicated Feeds that you've friended.
Those options alone help declutter your FList quite a lot, especially if, like me, you've got a ton of communities on your FList. It just so happens my communities tend to be pretty high-traffic, so it wasn't at all unusual for me to have an entire friends' page taken up by one community.
In addition, your drop down menu will also include any customized friends' group you've created, further slincing your FList view as you want.
Here's the link to click if you want to add it and try it out.
As I've said, I've been using it for the past few days and I'm very pleased with how it works. People are less like to get lost on my FList now.
Of course, I'm probably way behind the curve on this one. Everyone probably already knows about it.