If you are new to SEO and have seen the many adverts out there for directory submissions, it may seem very tempting. There are so many millions of directories on the internet, it's hard to know where to find the right ones for your market. Also, 1000 submissions for $200 might seem like a dead easy way to get round the process.
In my experience however, it's really important to have incoming links from quality sites that don't just spam 100's of links on badly optimised pages. An Indian company I used many years ago ended up submitting my site to over 500 directories with a page rank of '0', when all should have been a minimum of '2'. Also, the pages where my site was listed had nothing to do with my industry, it was a mix of anything and everything.
There are many free directories that I would recommend, with a few that are very important to be listed in due to their high Alexa rank and PageRank.
It may be an idea to look deeper into specialist websites that have a complete section dedicated to what you are offering. There are various techniques to do this, all of which I offer as part of an SEO package.