Here - in no particular order - are some links, and the experts associated with them, that you may find useful:

Ask Tom

Tom Kyte

JL Computer Consultancy

Jonathan Lewis

Method-R

Cary Millsap

IxOra

Steve Adams

Evergreen Database Technologies

Tim Gorman

Miracle A/S

Mogens N°rgaard

Oraperf

Anjo Kolk

Integrid

 Tanel P§der

Scale-abilities

James Morle

Juliandyke

Julian Dyke

 Go-Faster Consultancy  David Kurtz
 Adellera.it  Alberto Dell'Era