also, check out http://powerwurks.com/. according to wiki,
A John Karr, whose age, occupation, and number of children match that of John Mark Karr, apparently operated the website powerwurks.com around 1996. A Usenet post made by a John Karr on March 9, 1996 to the alt.support.loneliness newsgroup describes the purpose of powerwurks.com:
PowerWurks is a support organization for kids, teens and college students but all ages are welcome. We provide a safe and private environment where you can freely and comfortably express your thoughts and feelings on any subject. No subject is banned from discussion. All conversations are strictly confidential and that's a promise!!
The powerwurks.com domain name was inactive for several years, and on August 17, 2006 was purchased by Shawn Nemat. The site now contains various information attributed to John Mark Karr.
what i find most interesting is, the comparison between his handwriting and that found on the ransom note.