Everytrail - The GPS Travel Community is a website that allows users to upload routes and pictures of their outdoor adventures. As (and if!) it grows you would be able to check out a given hiking trail to get some idea of the views to be seen before you go. A nice feature is that you can view the maps on a USGS topo. Check out this page of a hike in Grand Gulch, Utah for an example of what the site can do.
Panoramio is another photo mapping service, but it is one to watch because it has been acquired by Google. There is now a Panoramio layer in Google Earth where you can view all the photos on this service. I created an account but have only unploaded one photo.
Finally, Flickr Maps is probably the largest collection of geotagged photos. The map interface is crude compared to the above sites, but Flickr's strength isedit the wealth of content with tens of thousands of tagged photos from the sites huge user base.
Edit: D'uoh! I forgot Google Maps "My Maps" option. If you have a Google account and are signed in, going to the Google Maps page will reveal a "My Maps" tab. Click on that and you can create your own maps with embedded pictures, audio, video, text and links. See for example this Route 66 map (choose the "My Maps" tab for the link) with oral interviews of old timers living along the Mother Road. This has enormous potential for historic trails like the Mullan Road.