I've included the backported packages (for i386 architecture) here, as well as the binary module for apache2 on the i386 architecture. I'm also publishing the -dev packages from the supporting libraries, which you might want to use should you try to build mod_auth_openid yourself.
I'm assuming that you're already running apache2 on a debian etch system. To do the basic installation, i think you need to take the following steps:
a2enmod auth_openid
/etc/init.d/apache2 restart
NOTE: This is still experimental! be careful!
Also, i found that it doesn't seem to interact properly with mod_php5 for me, though it does look like it works for CGI executions. I reported this bug to the upstream authors.
The package is also potentially under preparation for debian, but is hung up because of the classic GPL/OpenSSL licensing conflict.