Hulahoop, one approach that MAY work for you is to identify IF there are any directory listings linking to your competitors, the ones whose sites rank above you. I'd start there.
I wouldn't go looking for lists of general directories. Instead, I'd look for directories that specialize in editorial reviews of sites in your specific vertical.
For every rule there are exceptions. A general directory, such as those who pull their data from effectively clensed data sources, MAY be helpful - for example - in lifting local businesses in local listings.
I also wouldn't assume that an "effective directory" will be a stand-alone directory in all cases. It may well be the best directory to get a listing in is a one that is edited, in a non-biased manner, by an industry professional or professional group. Think "librarians" who may maintain specialized directories BUT look at the product to see if there's any evidence of links being sold, etc.
A "fast answer" ("Here's the list") will likely be a fast and dirty answer. If the answer is simple it likely is or soon will be an ineffective solution to pulling rank in an increasingly competitive WWW.
Lastly, depending on the value of the leads generated, a directory that may deliver even one sales lead a year may be worth at least the effort of submitting, if not the cost of paying for a listing.
Ultimately, the winner in the online world will be the one who is generating the highest traffic numbers from the greatest variety of relevant sites. In other words traffic from a variety of sites where a measure of "conversion influence" is built into the link-referral.
P.S. Forgive the edit. Requests for "lists", in any directory forum, tend to bring out the spammers, promoters and the same old same old lists of favorites. Bah. Humbug. ;P