I want to quickly identify potential mistakes created by OCR software. Where can I find a list of all Chinese characters that visually look very similar and might often be confused?
A friend and I have started to collect a list of characters easy to misread by language learners: http://code.google.com/p/eclectus/source/browse/trunk/libeclectus/data/similarcharacters.csv
List of 236 sets of commonly confused characters on Cantodict.
I started a web site to collect and help differentiate similar-looking Chinese characters: HorizontalHanzi.com
You can either search for a character to view a list of similar ones (e.g. search for 主 and get 王, 玉, 壬) or just browse the database.
Lists show the characters placed side-by-side for easy comparison as well as definition breakdowns and links to sites with more details about the individual characters.
My list of similar characters. https://kmccready.wordpress.com/2019/01/18/my-list-of-similar-chinese-characters/