You can never really have too many article submission sites. Both for researching topics and marketing, these sites are a great resource. The newest kid on the block is Howto.fm – an article submit site that focuses on how to articles and tutorials.
This site seems to be more focused on getting people to submit their articles as opposed to being an actual resource for articles, since the menu of tutorials is at the bottom of the page, and the first half of the page is dedicated to telling you why you should submit your unpublished articles to them. The articles have to be unique, in that they cannot have been published anywhere else on the internet.
Howto.fm has an attractive design, and is logical to navigate. Things are mostly laid out how you would expect them to be, so it’s easy to find what you’re looking for. Most of the articles I looked over are quality-written, and the authors display a knowledge of the subject.