I am also considering training. You are right - these forums are great and have helped me tremendously.
But I was thinking of additional training to improve my marketability.
ASQ does support a lot of training - and you may wish to consider joining your local ASQ section and attending meetings.
"Marketability" depends a lot upon your target company. Some companies put a heavy weight on degrees - if you don't have a degree, it may be worth attending evening classes or an internet program to work towards a degree.
The ASQ certifications add a certain amount of "marketability". Likely you will need to purchase a review book, attend certification classes at an ASQ conference, or if your Section is large enough it may offer certification classes.
Authoring articles for your local Section or ASQ Quality Progress may increase your marketability (build your resume).
Knowledge certainly can be gained through discussion boards like the Cove, but I don't think most companies will directly recognize it. I'll also point out I have a lot of materials for self review at
http://www.hanford.gov/rl/?page=1156&parent=1144 on statistical and quality improvement topics.