Juggling Links:

The best source for juggling information is the Interactive Juggling Database.
The previous best source is the Juggling Information Service.
The very american International Jugglers Association.
A good source of unusual props can be found here.

Individual Props:

Diabolo: Great site here and forum here.
Devilsticks: Sites here, here, and here.
Hat and Plate manipulation: The only site worth mentioning is here.
Coin manipulation: The site is here.

Jesters and jesting:

Probably the best site is here.
The Foolery Page is here.
Part of the book by Beatrice Otto can be found here.

Useful Companies:

Face Painting by Cathy Malcolm
Photography by Lee Marshall
Disco by Party-On
Fun Casino by Funtastic Casino

Local performance related clubs:

Wellingborough Magical Society