Does anyone know of a good way to find topographical maps for either download or purchase?
Google maps is free as in beer but doesn't usually show hiking trails. OpenStreetMaps is a free and open source site that works sort of like Wikipedia, and it often has good coverage of hiking trails, but the coverage may be somewhat hit-or-miss. For example, I've put in some trails for specific areas in California that are near my house or that I've visited.
The problem with both of these is that they don't provide topo maps with contour lines. Google maps does provide maps with hill shading, although IIRC they make it a hassle to print them, and you can't get features such as a UTM grid. There are some third parties that provide free topo maps in formats friendly to handheld devices, but I'm not aware of any that give global coverage. Here are some I know of, with links to a sample area in California so you can compare them.
If you just want color images of normal paper maps, then usually they can be obtained easily from national governments' web sites. Examples:
In my experience, the most practical approach is to get maps on paper, either by buying them or by downloading images and printing them out on a color printer. This has the advantage that it's cheap or free, and there is coverage of pretty much everywhere that I want to go. You can get maps with UTM grids on them, or draw in UTM grids. The UTM grid makes it possible to use them with GPS. An added advantage of the paper maps is that if your GPS unit isn't working (dead batteries, no satellites visible in the sky because you're in a deep canyon, ...), you can still use them. Yet another advantage is that they provide much higher resolution than an LCD screen at any given scale.
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