Dmoz and yahoo are considered Good Directories I guess. But what traits do the most successful directories have?
You may want to take a look at an article I wrote on the topic which might give you some things to look for. Distinctive Traits of a Quality Directory If you think anything was missed you can leave it in the comments there.
http://www.seobum.com/directories/153-what-makes-good-web-directory.html Also read this similar thread - http://forums.digitalpoint.com/showthread.php?t=1072506
IMHO, good directories offer something to their visitors, not just webmasters trying to raise their SERPs. If a directory actually provides value to people looking for information it'll probably still be alive 2 years from now. A link from that directory probably helps a lot more than a link from a low quality web directory that only has visits from webmasters. I try to find directories that Google seems to like (by ranking their content in the SERPs) and figure a link from them will pass link juice...and some traffic too.
My thoughts would be a well promoted one, one kept tidy and with the least amount of broken links etc. One thats got past the first year. One that doesn't make you wait after paying, responds to your questions, deals with problems urgently, gives refunds, allows for a decent title and has any useful options in this ever changing online promotion world.
- Enough categories so that there are not many listings (outgoing links) on the pages - Most pages indexed by google - Has backlinks to it - Has good PR (helps a little) - directory does not contain spam sites