I havn't done made a media kit before, but having looked at a whole bunch of media kits lately, my major #1 suggestion is to include your adversiting rates. The most important thing I want to know when investigating adverting possibilities is what is the bottom line.... why websites choose to exclude this crucial information is beyond me.
Yeah, I understand thats what they want.... instead I just dismiss them out of hand and go for oportunities that are more upfront and honest about thier rates.