A current example of what I consider to be a really well-written, engaging journal is on CGoaB at http://www.crazyguyonabike.com/doc/Nomads
I've been following it for a while, and eagerly await each new posting. The writer, Sue Gray, does a great job highlighting both the day-to-day aspects of bike touring, as well as capturing the essence of the many people they meet along the way. Definitely worth a read, IMO.
People create journals for different reasons. I usually write and publish mine with an eye toward providing useful info for people who may be planning the same or similar trip. That's a big reason I *read* journals before I go on a trip, as a way of preparing. Mine probably skew more to helping other travelers with info than a blow-by-blow narrative or character sketches (although I'd like to get better at that, too). I like history, too, so I throw some background info in. I'm a writer by trade, but I mainly do business writing (corporate comms and PR), so I'm sure that has something to do with the way I approach my writing.
You can see my journals on CrazyGuy at http://www.crazyguyonabike.com/directory/?o=RrzKj&user=briwasson&v=7
I'm in the middle of writing up my October tour of the GAP, but I have it partially posted above. Also linked from the page above are two journals on my personal website that I did for my bike tours in Europe, as well as a two "how to" resource web pages I created on finding B&Bs while touring in Germany and Austria, and a page on how to take bikes on trains in these countries. I plan to port them over to CGoaB soon, as it will give that info a much wider audience.
One other thing I'd say is to be careful how much personal introspection you put out on the web. A bit of it adds to the journal, too much of it might turn people off as it might end up sounding too much like therapy on paper. Also, the introspection you feel strongly while in the midst of the tour might not seem like something you want the world to read a few months after you are finished. To that end, I suggest keeping two journals, the one "live" one while you are doing the tour, with higher-level stuff, and a personal one where you record your deeper thoughts. Once you are done your tour, give it a few weeks and then review your personal journal and decide what stuff you want to add (if any) to the public journal.