I was working on a webapp to do just this. I find it frustrating too that if I check say once a day, and some of my followees have posted a ton that they clutter up the stream and I miss the one important update from someone that rarely posts
My solutions so far have been:
- Create separate lists for "low posters" and check those lists manually (a bit of a pain in the twitter app on phones, but relatively easy with multiple columns in Tweetdeck)
- Prior to that, using Filttr to at least block out tweets that contained username and 4sq (for example) for people who just always check in at places.
In the end the twitter lists ended up being the better solution for me, but no, I have not yet found a web app that really gives "weight" to tweets the way I would prefer