The issue has been hitting weblogs quite a while ago, and that’s why we have RSS. But stil, we need to narrow down the flow of information our aggregators feed us with daily!
One solution would be Bayesian Filtering in the aggregator.
As far as I am concerned, I will be providing category selection on my RSS feeds shortly (as weel as an aggregated feed for all my blogs). That should let you aggregate only the subjects you care about. ;)