I'm a little late to this party, but last week Pronet Advertising put together a list of 10 Things You Should be Monitoring.  Jeremiah Owyang added numbers 11-17 and Joseph Jaffe added numbers 18-23.  Shel Holtz even set up a page of the New PR Wiki where people could collaboratively add to the list.  I figured I'd add to the list based on my experience monitoring through our ImpactWatch platform.  Note that my contributions are mostly specifics building on some of the concepts others discussed.

(24) Search Term Volume.  Track how many people are searching for keywords that impact your company and watch how it changes over time.  This can be done using tools like Google Trends or through Google Adwords or Yahoo Search Marketing accounts.

(25) Search Term Rank.  See how high your company appears for key search phrases.  Obviously related to #24.

(26) Relevant Wikipedia Entries.  See how relevant Wikipedia entries are evolving over time.  You can subscribe to the RSS feed for entries so that the changes come to you.  If you decide to edit or complain, be transparent about it.

(27) Third Party Influencers.  For some, it is important to know everything certain individuals/institutions say about your industry as a whole.  For publicly traded companies, that might be financial analysts covering your industry.  For technology companies, this might be Walt Mossberg or Michael Arrington.  For others, this might include thinks tanks or trade associations.  Figure out who they are and read what they are saying.

(28) Key Stakeholders.  Employees were mentioned in the original list.  For some companies it might also be useful to track coverage of partners, suppliers, and other stakeholders.

(29) Press Release and/or Blog Post Pickups.  Many large companies seemingly produce a press release a day.  The effectiveness of these releases at actually generating press should be tracked so you can see if they are worth the time/effort.  Same applies for blog posts, if your company has a blog.

Note that I don't think every company should track every item I've listed above (or every item on the full list).  Some of the items I've added are only really relevant for specific industries.  But I think the cumulative list that has been developed could serve as a great starter kit for those implementing a monitoring program.