I've just added two things to BottomFeeder (dev update stream only) that make it easier to deal with your subscriptions. The first thing is a maintenance tool - select a cutoff date, and you can find all the feeds that haven't updated since then. Select the ones you want to delete, and you can blow them away.
The second one is a bit more complex, but possibly more useful. Here's a screen shot of the tool in use in my development environment:
What I've done is define a general category called "aggregators", with a bunch of search terms. With that done, all inbound items will be scanned for any categories I've defined - and thus made easily searchable by the categories I've set up. The "Categorize Now" button allows you to kick start the whole thing after you initially define a category.
That's something I've been pondering for awhile now, and I decided it would be a nice modification.
The "get rid of the old stuff" idea came from this post by Scoble. I realized that I periodically scan my feeds for old crap anyway, so having a tool do it for me would be loads simpler.