After few days of work and learning WordPress API the plugin is officially released. It has been posted to the wordpress.org and can be found at http://wordpress.org/extend/plugins/post-miner/.
While writing release notes I realized recommendations engine will work well only with English language. The reason for that is PorterStemmer library used by the plugin. PorterStemmer is very popular algorithm for stemming words and it works only with English.
I hope the community will like it and come back with some feedback (I'm sure many things could be done better).