I have been looking for some different article directories. While it's important to use the biggest and most established ones, it's also worth submitting to some smaller, newer ones. This does have SEO benefits, since Google does value a great diversity of locations for your backlinks.
And there are a lot of good lesser known article directories out there. They tend not to have high PR, however some of them do get lots of traffic.
Two things to look for when choosing these directories: If they seem to have unique, aesthetically pleasing templates, that is usually a good sign. The reason is that this implies that the owner is taking the project seriously and putting some real work into it. Chances are that even if it's new, without much content and traffic, the directory will still be around for a very long time. If it's just a cookie cutter directory, it's less likely to endure.
Also, check out the number of views for the directory's top articles. If there is a long list of these, and the viewer numbers are high, that's obviously a positive.
And have a look at the latest articles to have gone live. If you go back a week or two you can get a general idea of how many views a typical article gets per day, on average.