Tweetdeck is definitely a solution for as-it's-happening-shit-is-going-down noise filtering but for keeping an eye on topics long term I designed a side project which has been quietly filtering the half a billion tweets per day into more manageable digests. Perhaps you'll find it useful too.

I promise not to be offended if you feel you should delete this comment as shameless self promotion, but I honestly think it relevant: www.theHerdLocker.com