I'm looking for the best freeware/open source PHP-based API to access
the Blogger API (http://code.blogspot.com/archives/atom-docs.html). 
I've found a number of them, but many seem to be outdated.

This looks like it might work, but you have to install a package with
a lot of unrelated stuff.  I would think there must be a better and
simpler interface.
http://doc.b2evolution.net/0.9.1/xmlsrv/_blogs_xmlsrv_xmlrpc_php.html 

This would be perfect, but it appears outdated.  It refers to an API
key Blogger no longer requires, refers to hostnames/URLs that no
longer are valid, and I suspect it probably won't work as written
without updates.  If I'm wrong and you find proof, please let me know,
that would be an acceptable answer.
http://www.dentedreality.com.au/bloggerapi/

I found this list here of weblog tools, which list both of the above,
as well as some others, but none fit the bill, I think.
http://www.lights.com/weblogs/tools.html

I am not looking for a blog system but a mechanism to interact with
the Blogger.com system.