Links

Airfields
WWII Airfields
Twinbases - RAF Bentwaters and Woodbridge
Airfield & Aviation Memorials
Airfield Information Exchange
Debach Airfield Museum One of the EACS Endurance venues.

Calendars
Ian Hardy's stage rally calendar
racedates.net
Fairfield Motorsport

Maps
Centre Maps - cheap maps.
Map coordinate convertor, and links to MANY map sites for a given location. *Very good*
Latest OS map editions
ACME Mapper - full page Google maps. *Very good*
Large OS GB display with GPX import
Flash Earth - multiple map/aerial sources
GPS route planner
Open Street Map
Open Street Map viewer
GPX to Adobe Illustrator conversion service

Weather
Net Weather
MetCheck
XC Weather - wind forecasts
Live Storm Data

Car/Parts advertising
Motorsport Sales
Rally Cars For Sale
Rally Used Parts classifieds
Close Ratio
Race Cars Direct
Raced and Rallied
Rallying UK

Tyres
Tyre safety
UK tyre law
Carbibles.com: tyre bible

Towing
National Trailer & Towing Association
Also.
HSS Hire guide to using a trailer

Modification/preparation
Gear Ratio Calculator
Spring Rate Converter
Coil Spring Rate Calculator
Spotlight Wiring.
Automotive Converters and Calculators

Free Computer Software
The Open Disc - a collection of good open source software - includes the programs below.
Scribus - Desk Top Publisher
Inkscape - Vector graphics drawing package
Dia - another vector graphics drawing package
Open Office - full office package, including word processor, spreadsheet, database, drawing, presentation.
PDF Creator