More Semi-Related Tips and Tricks
On-Line Backups
use mysqlsnapshot (like mysqlhotcopy)
locking can be a problem (unless you use a slave)
use slave instead of master
decreased frequency when using replication
connection pile-up problem
Monitoring
knowing when replication dies
build a heartbeat system
Load-Balancing
Easy for slaves
Very hard for master
HTTP has spoiled us
Performance Tuning
test, revise, test, revise
my.cnf files are invaluable
upcoming book :-)