About.com
Lots of helpful advice on trailers, towing and hitching.
http://4wheeldrive.about.com/cs/trailerhitches/

BBC.co.uk
Tips from the Beeb on towing safely.
http://www.bbc.co.uk/motoring/ontheroad/safedriving/towing.shtml

CaravanAustralia.com
Towing tips and checklist.
http://www.caravanaustralia.com.au/towing.html

RAC
Tips on towing rules, loading your trailer, hitching up, maneuvering, snaking, stabilizers and more.
http://www.rac.co.uk/data_store/mycar/mi_towing_tips

The Volvo Owners Club
Members of the Volvo Owners Club impart their advice on towing safely.
http://www.volvoclub.org.uk/towing.htm