The Config Check module provides a report that you can run just before you launch a site to make sure that you've got all your Drupal ducks in a row. Among other things, it checks that:
Taxonomy Edge optimizes tree functions for taxonomies. It provides a transitive closure table data model for easily managing hierarchical terms. It was created to avoid recursive functions when fetching all children, and to avoid the not-quite-so-scalable memory footprint of taxonomy_get_tree().
The provided patch contains overrides for the core module Taxonomy in regards to taxonomy_get_tree() and taxonomy_select_nodes().
The Log4Drupal To File is built as an alternative to the watchdog interface, aimed at alleviating database load when logging events/actions of the system.