There are no better free sources on the open fiction markets than The Grinder and Ralan. Between the two of them, a short fiction writer can be kept up to date on the latest submissions windows and track work.
That said, I compiled a list of my usual suspects. Like both tools mentioned above, this list has links to submissions guidelines and methods, but compiles the info in one reference sheet.
Since the work has already been done, I present it here on the off chance that someone else might also find it useful.