I'm looking for a way to find "sub-trends", or words that are trending beneath a larger trend. For instance, say "#foo" is the hashtag for a conference. Searching for "#foo" only gives you a general overview of what people are talking about -- if "#foo" moves too quickly, it becomes really difficult to track disparite conversations at #foo.

If "#bar" and "#abc" are two different sessions at "#foo", one can find more specific information by searching for "#foo #bar" or "#foo #abc"; yet, how would one find out about the existence of these surrounding hashtags, i.e., sub-trends?

If you look at the screenshot for Peoplebrowsr, there's a panel that looks for "words surrounding [trend]," which seems to be exactly what I'm looking for.

Is there a way to accomplish this more simply, i.e., without paying $149 /mo. for Peoplebrowsr?

Thanks!

Update: Another service that can do this is Twazzup (click for example). The "Community" panel has some limited info on surrounding words; is there a tool that does this, but with more detail?