There are literally thousands of real estate directories in existent on the net and the question isn't how to find them and get links from them, but which are actually worth targeting. Just because you have a link doesn't mean Google will ever see it or credit it to your site. The best place to find worthy directories to target is doing some competitor analysis.

A great tool is OpenSiteExplorer (fyi, it's not free). Or you can use Google's search operator, link:somewebsite.com - that will give you a list of sites linking to "somewebsite.com" but the list is WEAK - especially compared to OpenSiteExplorer.

Shameless plug: I can help anyone with competitive analysis, it's what I do.

These are great valuable resources. Thank you all for sharing

I am checking out the free guide for sure.