Springer, publisher of a number of geo-related journals and books is having a promotion offering free online access to their Natural Hazards journal. The access is good for 30 days from October 22 so go check it out now. (Image copyright Springer).
The National Geodetic Data Center (NGDC) of NOAA has an online collection of photos of various geologic hazards. Many of the photos are from older sets of 35mm slides that have been digitized. They are free to use provided you credit the photographer and the NGDC as the source. The would be really useful for educators and for powerpoint presentations. The only drawback is that they are in TIF format and some of them could use some retouching. (Photo by University of Colorado, made available by NOAA/NGDC)