Peggy said that the scans were too light, so I used ImageMagick to run this command:
mogrify -contrast-stretch 5%% -sigmoidal-contrast 2,50%% -normalize *.JPEG
This has adjusted them to make the writing darker. They look easier to read now. I haven't uploaded all of them yet, but they're side-by-side with the lighter images in this collection:
NOTE: When you browse each set, you can click the "Actions" dropdown above the image and go to "All Sizes", which shows a much larger version.