To clear up a few issues
DMOZ Submission is worthwhile although the strength of a link has diminished over the years, Google have even removed their recommendation of having a link in DMOZ and the Yahoo Directory from their Webmaster Guidelines.
It is not common knowledge that you can have 2 listings in DMOZ
1. Site relevant category
2. Geographical relevancy
Affiliate Directories There are many directories that populate their listings from DMOZ, this number grows regularly as submissions are seen to be of good quality.
The Future for DMOZ Due to unethical practices from editors and Google's change of stance towards the Open Directory it appears the directory will eventually sell out to BOTW.
Yahoo Directory Panic hit this directory 6 months ago, when all inner pages temporary lost their Google pagerank maybe a warning shot from the big G...lol, quiet expensive for a listing when you cannot see the benefits. I have worked out a method of generating a listing via a back door method, don't ask...lol
Business.com Similar situation here as with Yahoo, an expensive link with not much guarantee that it's helping.
Both Yahoo and Business.com deliver very little in terms of traffic, I generated approx 25 visitors from the pair in a 12 month period.
Worthwhile Paid Directories My own recommendations are
Webotopia Business Directory Directory and Search Engine JoeAnt.com Webmaster Tools & SEO Tools Ezilon UK & Ireland : Web Directory and Search Engine Directory Dolphin - Business Web Directory Today | KillerStartups.com Without doubt £20 spent on a link with
Today | KillerStartups.com is money well spent, I know you can submit for free, however paying is the best method, especially when you consider the size of the submission form.
Links From Other Sources There are many metrics that can be used here, pageranking, relevancy, age of domain, links on a page, indexed, not indexed etc etc. The truth is it's very difficult to ascertain what's a good link and what isn't, even for the experts.
I spend 4-6 hours per day building links for my clients, the sites are ranking highly, so it would appear to be a worthwhile practise.
Conclusion Professional link builders spend years building up a quality database, although they might give the odd snippet of information, they are not going to pass on the fruit of their hard labour to all and sundry, rightly so.