You should suggest the site once to the single best sub-category that you feel is relevent to the site. If it is listable and would be better suited for another category the editor performing the review will move it to the most appropriate category.
However if the site in question (since you didn't mention a url) is one that has already been discussed (exhaustively) in these forums, then I seriously doubt the outcome of a review would be any different from any of the previous ones and therefore it would be pointless to attempt a resubmission. This of course is just my opinion since only an editor with permissions in the submitted category can review and make a decision on any suggestion and I do not know either the site your are thinking about resubmitting nor its current or previous circumstances.
If you feel the site meets the guidelines and is listable, you can submit it once to the single best category you feel it should be listed in and wait for a review to take place. You are free to do so, just as the reviewing editors are free to reject and delete any suggestion if it doesn't meet our listing criteria.
Hope that helps.