Duotrope, a website for finding places to send stories and novels, recently decided to move access to their core functionality behind a paywall. The reasons for this are explained on their site.
To replace the loss of Duotrope for the casual user, Diabolical Plots (who have a good write-up on the situation) have decided to introduce a new marketlist/submission system, which they call the Submission Grinder.
I have played around with this new tool and though it is in early stages, it is functional, with a submission tracking system in place and many writing markets available. Of course it will only continue to grow with use, and requires more writers to start using it for the submission data to be relevant. So if you are looking for place to search for new markets for your writing (and/or want an online submission tracker), check it out.