I'd be careful where you decide to backlink; Google can penalize your site for listings on bad directories. I found this useful guide before:
1.General in subject matter - This isn't a bad thing on its own, but it's certainly a signal that you may be getting a manipulative directory . While there are a few good general subject directories that Google probably does want to count (Lii, Yahoo!, DMOZ), there are far more who simply build general subject because it maximizes potential revenue (as anyone can apply).
2.Anyone can get in - If you don't filter out low quality, spammy websites from being listed in your directory, even a pretty badly built algorithm can easily spot and remove you. Besides which, Google has been on a tear for years about bad links and bad neighborhoods and how they use the sites you link to as a signal for spam identification.
3.Marketing to Webmasters - If your forum signature at Digitalpoint (sorry to stereotype, but it's just so true) contains links to three directories you own, you're probably in possession of three obviously manipulative directories. I'm sure there are a couple exceptions, but if I were Matt Cutts, I'd just tell one of my quality control guys to go spend a few days trawling DP for directory domains.
4.Promoting Search Engine Link Value, not Traffic - The great majority of the domains I listed use phrases like "search engine optimized" or "high PageRank" or "highly ranked" to describe their directory. Once again, this should be a clear signal that you're not selling listings in a directory, you're selling links that are supposed to manipulate the search engine rankings.
5.Use of Manipulative Link Building - Since the general directory industry seems to pride itself on toolbar PageRank, there's a lot of very shady link building tactics being employed by many directory owners. Sponsoring blog template themes, buying links at crappy directories (I know, the delicious irony of it all is hilarious), putting out junk press releases, releasing link-passing affiliate programs, joining webmaster forums that allow signature links, etc.
6.Stuffing Links & Content to "Look Natural" - It's rough to see the effort that many directory owners put into trying to "appear" natural, by adding links to government and education resource websites, major media sites, etc. A lot of the time, it's really easy to spot this "looking natural" business over an actual, naturally built directory. It's usually by category - the section on social sciences is filled with a few great sites, while the page on Minnesota DUI Lawyers looks a little funny.
7.Setting up "Premium" Sponsorships - When directories have a higher price you can pay for "extra links" or a higher placement on the page or assurance that you'll be linked to in every category, that's a decent sign that Google's spam team is going to come calling one of these days.
8.Interlinking with Other Directories - If I can buy entry in your directory, along with three other directories for "one low price," I'd probably be better off burning those twenties for warmth (or, you know, trading them in for $19 Canadian).
9.Common Popular Links - When I look through a directory's "most recent additions" and see a cosmetic surgeon, an Internet casino games site, a UK mortgage property, and a Pennsylvania health insurance provider, I can be relatively assured that any decent, self-respecting search engine probably wants to yank the link value pretty quickly.
10.Bid for Links - This has to be the most obvious link manipulation ploy I've seen in a while. How could you honestly think that search engines would want to count those links? It's like the eBay of spam, only without negative feedback.
11.Multiple Links with Your Choice of Anchor Text - I shouldn't have to explain this one - if you can choose your anchor text and point to several pages on your domain from your listing, it's pretty clear that the directory isn't targeting humans.
12.Banner Ads from Your Directory on SEO Sites - It's like waving a flag with a voice-activated, wind-powered speaker that yells "Ban me! Ban me!" Sure, you might get clicks and money and submissions, but you've gotta know that search quality team members read SEO blogs, too - so if you do this, make sure your directory is ready to be manually reviewed by search engineers.
13.Demanding Reciprocal Links - If a directory requires that you link back to them in order to be included, or that you can link to other sites they promote in exchange for reduced payment or free inclusion, it's almost certainly trying to manipulate search rankings through linkage.
14.Choose Your Own Anchor Text - Not nearly as fun as Choose Your Own Adventure, this screams "manipulative and built for rankings, not humans." DMOZ & Yahoo! and lots of the more legit directories will only use the company name or a site description, rather than allowing the user to decide on their own anchor text. This is particularly egregious when the directory lets you link to 4 or 5 pages and pick the anchor text for each link.
Source post:
What Makes a Good Web Directory, and Why Google Penalized Dozens of Bad Ones | SEOmoz