Many people still find directories a useful resource when looking for things on the Internet although with the arrival of social bookmarking sites they have stiff competition. A well maintained directory can not only be useful resource for any site visitor but also provide valuable inbound links to a site.
Page rank is still valid for Google at the moment, although it seems to have less value now, and is an important aspect in deciding which category your site should reside in a directory. An example is could be if an automotive directory has a sub category of custom parts and accessories with 11 links in it and another sub-category of paintwork with only 4 links in it then paintwork would pass more page rank to your site. However something to bear in mind is that relevance also plays an important part of the category selection.
What is a good directory?
To determine whether it is worthwhile register your URL to a directory it is probably worth asking yourself whether whether in the absence of a search engine you would personally use that directory? If the directory is full of broken links or irrelevant or poorly written content then it is unlikely to be worthwhile. The good folk at Google sometime manually adjust their index to remove or lower the value of anything that appears to be a ‘spammy’ directory.
There is a lot of debate over paid and free directories and their value as a web-resource. Both types of directory should have equal value in the face of a search engine however paid directories tend to be better maintained as they usually have a team of moderators checking each submissions. Free directories generally depend upon volunteers which lead to people playing the system to allow their own links to be submitted to the directory.
There are many directories that are recognised as ranking well in the main search engine algorithms but the main two that most people will come across are DMOZ and the Yahoo! directory.
The DMOZ or Open Directory Project was founded in 1998 and was created in the spirit of the GNU software foundation and was intended to be a completely ‘open’ directory maintained by a team of volunteers. The index is well maintained to this day and is regarded by Google as a trusted source.
There has been a suspicion for some time that Google now uses a trust rank to filter out spam from its index. It is believed that it does this by selecting a few known good sites from around the web which are known to have a good stance on rejecting spam. The trust rank then emanates from these sites and filters through the Internet giving each site a trust rank in a similar way to the page rank.