At the moment, the longest video you can upload to YouTube is a mere 15 minutes. But that's not going to be the case for long, at least as long as you follow the rules.
YouTube has announced that it will get rid of the upload limit for "selected users with a history of complying with the YouTube Community Guidelines and our copyright rules." So if you've been trying to upload entire movies in many parts, you aren't going to suddenly be able to upload one big movie, you awful copyright abuser. But if you've been a good little uploader, you may soon be able to finally upload that 230 minute comedy video you've been working on.