Can I post the same article to multiple directories/websites, or does it have to be unique each time? Obviously for the purpose of backlinking and not looking bad to google. Also considering google's new algorithm, if that matters at all. If the articles need to be unique, it is much more effective to write small articles to major blogging sites than blog directories, right?
Sure you can, many directories accept non unique content. Off course it would not be as effective as unique one as your article may not get indexed meaning your wont get backlinks from it.
You can do that but try to do some minor alterations while submitting so that they don't decline your submission
You can submit the same article to article directories, so long as the article directories will allow or approve the articles. But I wouldn't suggest you do that because it is counter-productive. The articles will not be indexed and so will not get you good backlinks. Google recently changed their algorithm and slammed content farms so submitting the same article on various sites will not get you anywhere. You may want to submit the original article to an article directory, spin or re-write the original article then post the re-written ones to other article directories. Posting original articles is much better these days so do that whenever you can. You can find more tips on article submission here.
I won't suggest to post the same article in multiple directories it is of no use just we will enjoy the sudden back link but after some time Google stop caching these article and it is just a waste of time. Instead of posting one article on 100 articles directories it is better to post the article in one authentic article directory and in continuous intervals contribute your article to many available authentic article directories. This will help other and chances of getting link baits from authentic websites are higher. Thanks, AG
Just think about it, natural progress of a good quality article on the net is that people pass on the article. Yes, you can submit it multiple times and it does help. Just try and submit it to quality directories, or on the blogs of friends.