As recently promised on the vufind-general list, I have created a new branch in Subversion to aid development of Dewey Decimal support in VuFind:
This is based on the current trunk, and as of r1934, I have added basic support for indexing Dewey numbers at ones, tens and hundreds levels. SolrMarc is currently reading call numbers from 082 and 083 fields, but this is easily customized if you store yours elsewhere. Also, since I expect that this branch will eventually merge back into the trunk, things are configured with Dewey disabled by default since I expect the majority of users will not be using these features. However, to try them out, you can easily enable them by editing import/marc_local.properties and web/conf/facets.ini.
I'm going to do more work today and next week to start adding Dewey support to the Browse module -- I'll post again when this is ready for testing.