I intended this to be a comment to Dave Warlick's post on the subject, but his comment system won't accept my submission. I think that this post shows the futility of anyone trying to claim credit for the term.
I have found a reference to a 'personal learning network' in a document dates April 8, 2000, by the Treasury Board Secretariat, Government of Canada. http://www.tbs-sct.gc.ca/pubs_pol/partners/workreport8-eng.asp This use, although dates, is consistent with uses of the term today. "Personal Learning Network has PC based, multimedia learning activities that employees can tailor to a learning map.
There's another resource, dated 1998 (but the metadata says 2001-08-05, which is still pretty early), Building Your Personal Learning Network, by Daniel R. Tobin http://www.tobincls.com/learningnetwork.htm
In 1999, something called a 'Personal Learning Network' actually won an award for a company called Quisic. http://www.quisic.com/qweb/company/about/awards.htm
Another 2001 reference is the book, 'The Learning Web', by Gordon Dryden, which has a chapter titled "Your personal learning network". http://www.thelearningweb.net/
This page, apparently from 2002, refers to "building each student’s personal learning network." http://www.prel.org/products/Products/promising-pract4.htm
Milton Ramirez (tonnet) uses the term on June 10, 2003. "Most importantly, thanks to Education & Tech we have been able to build the most respectable Personal Learning Network in Education, we had the opportunity to start writing for the most important international network of bloggers and citizen journalists, Global Voices Online." The site is down, but available through Google Cache. http://tinyurl.com/yem2n8a
The first reference from George Siemens I find is September 30, 2003. "Most of us belong to more than one learning community. These multiple communities form a personal learning network. If a learning community equates somewhat with a course, then our learning network is equivalent to a degree program." http://www.elearnspace.org/blog/2003/09/30/learning-communities-and-learning-networks/
He follows up October 17, 2003. "A network, in the context of an ecology and communities, is how we organize our learning communities...resulting in a personal learning network." http://www.elearnspace.org/Articles/learning_communities.htm