I've just started using SubmitterBot to submit my blogs for free to directories and get back links.
SubmitterBot is what they term a semi-automatic directory submission tool. You just register for free and then add the URLs you want to submit. When you press Start Submitting, you are presented with each of the 446 directories one at a time, you decide whether you want to submit to it or not, then choose the category and submit your site.
It's semi-automatic because you choose which of the directories you want, along with the category in each one. They say it should take about 30 minutes to do it for each of your sites, but I found it actually took a little bit longer - but maybe that was just me.
It's free and it creates new links, so I'm hoping that it's going to be another tool to build up back links, Page Rank and traffic.