Consider these links a jumping-off place. You can find many more links by searching the web for particular canals.
I welcome any suggestions for additional entries.
NOTE: most canals will have a page on wikipedia. They are ordinarily good pages, but I have not tried to list them here.
Paul Smith's 1999/2000 trip reports on the Erie, Cayuga-Seneca, and Oswego canals
Immortalized in song. See Low Bridge (song)
Boat hire firms:
Transiting the Erie Canal - this is a google search; first 20 links may be useful
The Erie Canal, by Frank Sadowski - a plethora of historical material
The Engineering of the Erie Canal - No longer available - part of the Ohio University Online Master of Science in Civil Engineering program [Thanks to Kevin Powell for finding this one.]
Time lapse trip through the Erie Canal - video; 7 days in 8 minutes!