I had the same problem as you and here's how I solved my problem. Bear in mind that while this worked for me, it's not a "one size fits all" situation.

Clean your subscriptions

• removed most of my feeds
• kept the ones from authors with really great content, which I read 90% of the time
• kept work-related feeds (security updates, partners feeds, competitors feeds, etc) - I'm thinking of moving this to a separate account

Get curated sources

• follow the relevant people in your fields of interest on Twitter. Even if you subscribe to their blog or similar, they will certainly share content of your interest, effectively curating content for you even if it's not their own
• use a tool like Cadmus for seeing what content from your timeline (i.e. the people you follow) was most active (retweets, etc) - those are what you are looking for, mostly.
• search for relevant digests of content. For instance, I'm into startups and found StartupDigest to be a great way of keeping up with news on several related topics - they send weekly newsletters on a fixed day, with links to relevant content from that week.

As a final note, this is obviously not the best way to discover "hidden pearls" of content, but it's a time-effective way of keeping up with great content.

Cleaning out any feeds with a low signal-to-noise ratio and relying more heavily on curated sources is excellent advice that should reduce the number of feed items overall and decrease the volume of uninteresting content.

Given that you've done all of that, the remaining improvements are going to be in workflow and how you interact with your reader. My over-arching philosophy is that I process my RSS feed items similarly to how I process email. The options are different (e.g. I respond to lots of email, but feeds, not so much), but the concept of processing an item once and decided what it means to you are common.

I also use Google reader and my basic workflow is simple.

1. Most of my processing is done in the Reader web app on my iPhone. I like this option because it allows me to process feed items in any idle moment: while standing next to the microwave waiting for lunch to warm up, while in a line, while waiting for a meeting to start, etc.
2. I stay in the "all items" feed and scan the titles. My nosiest feed is Slashdot and 70 percent of the items never get expanded beyond the title.
3. If something is interesting then I expand it for additional reading. If it's short and the whole post is right there in Reader I may finish it right then. Daring Fireball is a great example of a feed with lots of small updates.
4. If the post is long, contains links I want to follow up on later, includes non iPhone friendly content like flash, or if the full post requires me to go to a separate page, then I star the item and move on.
5. When I get to the bottom of the screen, I tap "mark these items as read", which does exactly that and then refreshes the feed, loading the next 15 unread items.
6. I keep doing this until I'm done processing or bored with it.
7. Then when I'm in a reading mood I switch to my starred items and read in more depth (at a computer if need be), clearing the star when I'm done.

So I basically use my all feeds list as unprocessed items and my starred list as a place to store future reading material and feed items that I haven't extracted everything I want from yet.

Most of my feeds are pretty quiet on the weekends, so any backlog that builds up during the week typically gets cleared by then.

About once a week I cull through the starred items list and clean out anything that was interesting at the time but that I'm no longer interested in.

Now if Google only changed "like" to "+1" and added an option to share a feed item via Facebook or Google+ (i.e. changed the share function from "share within reader" to "share within G+/FB" my workflow would be further simplified, as I wouldn't need to click-through to the article and paste the link.

Try out offline readers like Instapaper or Pocket.
This helps in multiple ways:

1. While reading the RSS feeds, you can have a quick decision on whether you want to read the whole article later at leisure, or do you think the summary itself is good enough for you to mark it as read.

2. This allows you to work in two modes - the accumulation mode where you are just going through your reader feed. Almost like the GTD Inbox technique. The consumption mode is kept for later when you have time just to read things.

3. Once you send it to an offline reader, you can then group the content in multiple ways. Either by subject, site, date etc. This allows you to read things at different times

4. And yes - if you see that you are "adding more to read later" and keep accumulating content via the reader, you do have to make a conscious choice between collection and reading.

I have been using Good Noows for my personal use.. It has a list of popular RSS sorted by categories and you can select which RSS you want to view or not. You can also create your own categories. I have created "My feeds" and added some frequents websites I visit daily. It also allows you to view the content in various different layouts suitable for you. Plus it has integration with instapaper for readlater and keeps track of what you have been reading.

Try it out.

All these answers are workarounds but don't really adress the question that was posed. There's no real way to stop your RSS feeds from becoming a mess and there's no real way to stop information overload. Filtering tools slow this down but aren't enough. You can do your best to pare your feeds or followers but at the end of the day info overload is a symptom of overconsumption. We need tools that don't show us how many unread we have and filter down to what keeps me informed and healthy.

That's basically why I'm building Skim.Me (http://skim.me). To make your daily browsing routines more productive or at least FEEL more productive. We do all setup, organization and management work for your favorite site and app sources so you can browse no-reply emails, weather, news, social media, ecommerce, finance and more without leaving our web app in timed batches throughout the day.

As you browse we manage a “done” list for you that can be toggled to a “to-do” list for browsing that’s algorithmically controlled. It’s a great user experience that shows you what you’ve accomplished and never how many unread you have.