When you do a Twitter search you can use # in front of a term to eliminate that term (including other hashtags).
If you have a search that you are interested in keeping up with, you can put the RSS feed for that search in your reader (it's a link on the right-hand side of the page). Since my reader and I are fairly inseperable, it's a pretty good deal and then I also don't need to 'follow' everyone who is also interested in similar things or read all of their unrelated content. Works for me!
Objectivists should have their own hashtags. How about #obj?