Just two quick suggestions to add to the mix:
Technorati - type in your brand name and see what's being said in posts across many different sites. I know it was mentioned about RSS feeds -- great idea. Another method is the second suggestion :
If you notice certain pages appearing on the front page that mention your site (the first page is what you should be most concerned about if someone google's your brand name), use a monitor tool that will automatically inform you of any changes made to that site's page. Such as, if there may be follow-ups after your rebuttal to a negative post or claim.
There are paid and free services that do this for you.
monitor web site changes - Google Search
Good luck!