I want to start a mobile blog to post pictures from my Audiovox 5600
cameraphone.  I am an AT&T wireless customer (and have not yet rolled
over service to Cingular). What are the different types (models) of
mobile blogging services available?  What are the most popular mobile
blogging services available in the US?  Which one in particular would
you recommend I start with, given I am new to blogging?  What are the
associated fees/costs?

I would recomend that you use TextAmerica. It is a rather simple and
free mobile blog (or moblog). I would say that this is probally the
most popular moblog in the states. The reason is that it is very easy
to use and has lots of features. Although it is free you have the
option of upgrading for 69.99 a year. This upgrade allows you to
customize every aspect of your blog, but unless this will be a blog
that is meant to be seen by a huge audience, the free version is fine.
Hope this helps

By the way, the link is:

http://textamerica.com

There is a company called http://www.picostation.com/ that has a
mobile blog software application called "picoblogger", and its free.