Does anyone know of a good way to find topographical maps for either download or purchase?
The United States Geological Survey (USGS) has topographical maps arranged in the typical 7.5 minute quadrangle format, available for free viewing & download online for all of the US.
In the UK your best bet is to use the Ordanance Survey website where you can purchase maps: http://www.ordnancesurvey.co.uk/oswebsite/
I've used the getamap feature which is great at creating your own maps! Which is useful if your hike goes over several map boundaries - often the case in the Lake District!!
You can also use Bing maps which has OS map data down to 25000:1 for the UK!
I use www.mytopo.com to order waterproof topo maps to take camping with me.
They also have a good interactive online tool which you can use to find a specific area.
Check this link out:
It contains this and many more countries:
University of New Hampshire Map Library
NATIONAL PARK SERVICE MAPS ONLINE
USGS (THEMATIC) MAPS ON DEMAND