The submission posts here today gave me an idea about providing links to online market guides for writers. These are the ones I have used and are very reliable.
Ralan.com - This one is provides info on science fiction and fantasy more than horror, but you will find the occasional horror submission call. Ralan also provides writing tips and other useful info that’s right on the home page.
And through Ralan I found Dark Markets - which is The Best submissions guide for horror, imho. DM also has writer interviews from time to time.
This next one comes from Alliterator - The Grinder - is also a great source which lets you track your submissions. Pretty neat!
I’ll be re-posting this from time to time for anyone interested. And if you know of any other writer resource websites, please feel free to add them in the comments.