So if you want to know, take a moment and read the Release Notes. https://cwiki.apache.org/confluence/display/OOOUSERS/AOO+3.4+Release+Notes
You'll see two sections, one 'New Features from the OpenOffice.org 3.4 beta' and one 'New Features for Apache OpenOffice 3.4. So LibreOffice 3.x is based on the same source code for the first section since they forked it under LGPL and worked on that. Same thing with the Apache OpenOffice community. The second section describes the features added by the Apache project, now available to the LibreOffice project if they choose to build it in and presumably re-license under MPLv2 which appears to be their preferred license going forward for new contributions from their community.

Subscribe to their lists. http://incubator.apache.org/openofficeorg/mailing-lists.html
Some ideas here: https://cwiki.apache.org/confluence/display/OOOUSERS/Help+Wanted
Also it's fun to write extensions...which are hosted over on SourceForge.