I know zilch about seo, but I voted for the most popular one, surely having full relevant words helps? I say this cos my bid directory ranks no.3 against some stiff opposition for 'bid for placement'. I can only put it down to the domain name: http://www.google.com/search?q=bid+for+placement&ie=UTF-8
The second one is the better of the lot considering your intended purpose and it is a matching name. I am not a big fan of -ies and -ing postfixes. Big chance of making mistake in that.
Voted for deeplinkdirectories.com Only #1 and #3 makes complete sense. Rest are either grammatically or logically incorrect. I though like #3 and voted for the same. Almost everyone voting for #3....And you had a confusion
If it were a deep link directory itself, I'd agree with you, but instead I got the impression it's a "directory of deep link directories," meaning if someone's looking for a list of them, they'd more likely search for the plural than the signature. And naming it with the singular makes it come across that this directory itself would be a deep link directory, rather than a collection of them.
I know its kinda side track but i had a dream yesterday that I built a directory of directories and it was a big hit.. When i woke up, I still think it is a very good idea.. too bad i dun have time for it as its so close to my wedding now.. But if someone who wants to be my partner for this project, with the knowledge of php and Mysql, pm me and maybe we can do something about it. And Rob, my vote of www.DeepLinksDirectory.com ... might not make too much sense to you, but i m glad someone shares the same view with me.
www.DeepLinkDirectories.com also i dont agree with the idea that you will make a mistake with the directory name either since its not as if u are gonna need to remember it from a commercial or radio its a link and you will instantly remember if its the same site from the template even if you at first unsure imo anyways
I would agree that the .info is a good way to since a directory is a source of information, but I don't think it will matter since most will support it either way.
23 (DeepLinkDirectories.com) vs 8 (DeepLinkDirectory.com) Rob. Are you still looking for suggestions??