http://wpmu.org/scaling-wordpress-wpmu-buddypress-like-edublogs/
Interesting write up by James at Incsub on how they handle scale on edublogs. Some good advice although a little light on specifics, a good starting point for research.
http://db-tools.wpmudev.org/db_servers.php
Tools to automatically generate multidb related code such as create database queries, db-list.php files and so on.
