I am an enthusiastic readers of countless WordPress(.com) blogs. It is possible to simple way (through the API instead of screen scraping) to obtain a catalog of posts (with date, title and URL) and so i do not have to by hand wade with the back archives?

The only real public 'API' you will have available may be the RSS (or Atom) feed, but this usually only shows the ten newest posts.

The XML RPC could have been the choice, but I am certain requires authentication.

Apart from that, while you say, your only option is some elementary type of screen scraping.