Is there a WP plugin that posts full articles on my site?

I'd recommend you focus on just getting the content put on your website first and don't worry about article directories at all.

You could potentially get the article posted on a directory at a later date but most of the higher end directories would mark this as an article already published and decline it.

I'm not a fan of article directories personally - sure you'll get a back link and you can hope for some traffic but article sites have declined since Google has given them a constant beating with algorithm changes; that back link probably won't have much power either because it's going to be a fresh page.

IMO the majority of traffic on these sites is the wrong type anyway, it's mostly people researching for other articles and article writers/authors - your content wouldn't be reaching the right people.

Article directories should be avoided by authors too - if you really want to put yourself in front of the right people you'd be better off putting together an ebook with a series of blog posts (high quality of course) and getting it on Kindle or using smashwords.com.

Don't get me wrong though, article directories used to work well but as Bob Dylan once said; "the times they are a-changin".

Just my two cents, others may not agree with me on this.

Try the Professer's advice - look in the plugin repository. There are a variety of RSS scrapers in there.

Since your professed intent is to usurp the benefit of other peoples' work, I can't in good conscience wish you luck, though...

My problem wasn't the idea that you were going to legitimately post articles other writers made freely available for the purpose. My problem came from this bit:

As sports officials are wont to say, "Upon further review..."

If the author of the article on the directory is dumb enough to post to that directory without first getting it indexed on his own site, tough luck for him.

In other words, if a writer is doing things right and getting the article indexed on his site before offering it for syndication, your plan won't hurt him in the long run. So have at it with a clear conscience, as long as you stick to your guns and publish according to the directory's TOS (links included, no changing the article, etc.).