Charles has gotten me hooked on Article Marketing Robot. 5 Day free trial that inserts 1 link promoting the product. Based on his recs in a private thread, and my results from the trial period, I've been sold on using it. Most of my submissions using the tool have ranged between 420 and 550 successful submissions, built-in spinner, etc. Only tool I've used that I've seen SERP movement in less than 24 hours if I was already ranking to some degree for the keyphrase.
The Ultimate Article Marketing, Spinning & Submission Tool *EVER*