First prototype done

Forgot a little guide to testing the module:

You'll first have to apply the following patches to the apachesolr module:
#527566: Solr_Base_Query: escape special characters before using field name in RegExp
#526344: Remove apachesolr_read_only check from Drupal_ Apache_Solr_Service::_sendRawPost()

Then you'll have to run a solr instance with the schema.xml and solrconfig.xml files provided with the module. (An elaborate guide to this can be found in apachesolr's README.txt file.)

Then just enable the module and go to Administer > Site configuration > Apache Solr RDF. There you can enable indexing for the different contexts. If you want more than one context indexed at the same Solr server, the solr_* and the id setting have to be the same for all of them. The names should be equal, too, but it's just pointless (and no error), if they aren't.

At search/apachesolr_rdf you should now see all enabled searches, by running cron you can index the according resources. At the moment, only a simple key search is available, but this should change soon.

Another little point I forgot: You'll also have to copy or link the sindice-url-preserving-tokenizer.jar file to $solr/example/solr/lib before running the Solr instance.
But that should be about it.