What is a Good Directory?
In fact it is not so easy to answer this question, probably there would be many features that we could not think of in a perfect directory, though there are some things we definitely know about this.
Over the past few years the number of web directories increased amazingly. The main reason was; there were good scripts developed and published(such as the one we use) so now it does not take more than 10 minutes to build up a directory which looks pretty professional(thanks to template editors) and mostly for free. Another reason is; many people see directories as a good way to make money. But...
If we go back to our subject, a good directory is a guide to serve good quality content to web users. Yes, we have well developed search engines to hunt down what we look for, however even todays' so-called best search engine Google's bot can not fulfill the needs because it still is possible to trick a bot and make it see pages in a way it not actually is. So this leads to todays SPAM-full search results covered within almost every search engine(not to mention little cute SE's)
So this gives us the idea; no matter how much web technologies improve, a human review still is necessary. There are countless directories on the internet, so we would think of the biggest ones first, right? Surely. DMOZ (Open Directory Project) is todays' one of the biggest human-edited web directories, these giant directories usually work with "so-called" volunteers to edit a huge amount of categories. But, for the sake of god, why would someone help you build something without getting anything back? Maybe you think there are people who work for "directory charity" but i assure you there is.. none . I have seen so much about those, asking for $$, adding their own sites and disappear etc. so basically those big directories are simply a source for SPAM.
Pagerank of a directory is oftenly used to sell links. However too much scam is going on about this issue.
If you decide to buy a link from a directory or elsewhere considering its' PageRank, make sure it has valid PR value. There are 2 ways to fake pagerank, i'm not going to detail them here but first you should check via Seo Tool's Fake PR Detection Tool
When you do, you will see an image like this only if PR is not faked:
Another way is; some high PR domains drop due to expiration and some people buy them and turn into link selling websites/directories. SEO Tool's tool is unable to detect this. So you should go make a WHOIS search to the domain and make sure it was created before Last Toolbar PR update.
Just so you know; last update was on 15th of April, approximately repeats on every 3 months.
Good luck with your project!