Thanks to Inkpot, I have now signed up to this wonderful writing resource - Duotrope.
It's an up-to-date list of writers markets, with a good search facility to help you to identify markets of your chosen genre, length, payment, etc. It also provides statistics on the min, max and average response time, plus on the likelihood of acceptances. These stats come from writers who register with them and record details of what they send where, when they submitted and heard back, and whether they were accepted or rejected.
Not only is the information provided very useful for writers but their submission tracker is excellent - making it easy to you to keep an eye on all your stories currently doing the rounds - I highly recommend it.
Currently it's free so if you're a writer, please consider donating to it to keep it this way!