LAST EDITED ON Nov-05-07 AT 01:24 PM (PST)
 
I'm not real big on article submission to create links, as I believe most of your content should be used on your own sites/domains.

However, I do believe that it can be a helpful part of your linking mix.

- Directory submission

IMO, you're probably best off just submitting to the top 3 article directories and spending the time saved using other linking methods:
My own experience has been that you need to submit to these
3 major sites:

www.EzineArticles.com
www.ArticleCity.com
www.GoArticles.com

Of course, if you have your own favorite(s) or have had success using more/other article directories, keep doing what your're doing.

- Selective submission

By this I mean that instead of posting articles to directories, you look for high quality, well-known and respected sites and offer guest articles.

You give the site free content and they give you free, high quality links back to your site.

To find sites that accept guest articles, try searches such as:
"keywords" + "guest author"
"keywords" + "submit articles"
...etc.

Here's a more comprehensive Google query I "borrowed" from Planet Ocean:
"your keyword" "submit * article" OR "submit * articles" OR "add * article" OR "add * articles" OR "featured writer" OR "featured writers" OR "featured author" OR "featured authors" OR "featured contributor" OR "featured blogger" OR "guest author" OR "guest writer" OR "guest blogger" OR "guest post" OR "submit * tutorial"

Getting some links from highly respected sites in your niche can do wonders for your links and your rankings.