The Bookseller
The online version of The Bookseller magazine is a window on the whole publishing industry.

The Society of Authors
The professional organisation for published authors.

SCBWI British Isles
The Society of Children's Book Authors and Illustrators is a great organisation where both published and aspiring children's authors can meet up to swap tips and trade info.

The writing consultancy of children's author Nicola Morgan, who also offers excellent free advice at her blog Help! I Need a Publisher.