San Diego Transit
http://www.sdcommute.com/

U.S.-Only Coverage:

Mapquest
http://www.mapquest.com/

Yahoo Maps
http://maps.yahoo.com/

Google Maps
http://maps.google.com/

Maps On Us
http://www.mapsonus.com/

RidePlanner
http://rideplanner.harley-davidson.com/en/RidePlannerMain.js

Rand McNally
http://www.randmcnally.com/rmc/directions/dirGetDirections.jsp

U.S. And Canada Coverage:

FreeTrip
http://www.freetrip.com/

Extremely Wide Coverage:

Maporama (worldwide)
http://www.maporama.com/

Map24 (U.S./Canada)
http://www.us.map24.com/

Map24 (U.K.)
http://www.uk.map24.com/

Map24 (Europe)
http://www.de.map24.com/

Map 24 (other)
http://www.google.com/search?q=map24

MSN Maps and Directions (U.S./Canada/Europe/Australia)
http://mappoint.msn.com/

ViaMichelin (Europe/U.S./Canada)
http://www.viamichelin.com

Europe-Only Coverage:

Royal Auto Club
http://www.rac.co.uk/

Mappy
http://www.mappy.fr/

AA Route Planner
http://www.theaa.com/travelwatch/planner_main.jsp

Traveling with Agip
http://www.agip.it/rmit/agip/program.do?lang=en&mncommand=home&programName=agip_toViaMichelinCategory

ANWB Routeplanner
http://route.anwb.nl/

MultiMap
http://www.multimap.com

More route planners, worldwide meta-site:
http://www.reiswijs.co.uk/routeplanner/routeplanner.html

Miscellaneous:

U.S. gas station finder
http://gasuphere.org/

U.S. truck stop finder (gas/food/sometimes lodging)
http://www.truckstopinfoplus.com/