Started a thread in General but some of these may be useful...particularly:
www.mappy.com or
www.mappy.co.uk look useful for European travel and will, apparently, calculate toll costs for Autoroutes (but not for bridges). Put the vehicle type in to get these accurately.
www.maps.google.comCovers UK, USA and Canada at the moment - and has v detailed satellite pix of US and Canada.
http://uk.map24.com/ 'is pretty impressive'. (Jimbo)
www.viamichelin.com 'Best Euro routing I've found ' (Dodgy Geezer) Apprently also has most of the fixed speed cameras in northern europe.

Update: there's also
www.viamichelin.co.uk which may be quicker to use from the UK.
www.rac.co.uk has a popular routing facility. It allows a range of routing choices (avoids, via's, etc) and appears to cover most of Europe.
www.bestbikingroads.com has European Biking Roads with maps and some GPS co-ords. Offers routes all over Europe and allows you to enter your fav routes.
Pocket GPS UK Safety Camera Database Also includes NL & FR. Not strictly mapping as such, but can help planning

(Splat!...you must be a very naughty boy

)
http://www.transportdirect.info/TransportDirect/en/ is a little strange in terms of routing but may have particular uses.
For the Franglais speakers

:
http://www.autoroutes.fr/index.php?lng=2 is a handy route planner for France, with info on tolls, travel bulletins/radio, weather etc. Note the name...it's focused on the motorways.
Not a routing facility, but information about roadworks in France, plus some bottlenecks
http://www.bison-fute.equipement.gouv.fr/http://www.uem-online.com/goie.html - ADAC/European Union of Motorcyclists motorcyclists maps...downloadable from the UEM web site.
Not particularly detailed or high quality (maybe a little easier to read thru a tank bag?), Some interesting routes...eg map 7 - the Ardeche gorge.
There's Multimap and Streetmap too - I'll add 'em later and extend this to 'PC' based software too.