There are some lists of similar characters on the Internet. Nevertheless, I suggest you to make your own list as you go along. Why?
First, because similarity is a gradual, not an absolute concept;
Second, because similarity is a subjective concept, not an objective one;
Thirdly, because two (or more) characters may look almost identical, but one of them may have a very high frequency of use and the other(s) a very low one;
Last but not least, I think it could be more rewarding, if not fun, to make your own list.
@sobriaebritas thanks alot for your reply... yes i think you are right, because like you said this is a subjective concept, not objective.
bytheway i realised recently that pleco already has this function for similar words (when you search a word, in CHARS and WORDS parts it shows all the similar characters by similar strokes and meaning. i just bought the pleco bundle recently i don’t know if they had this function in the free version of pleco too or not but anyway it’s a really helpful function especially for someone like me with lower level in chinese.