"Submission Guidelines for every Comic and Manga Publisher in the Universe"

This is a list compiled almost two years ago, but it's chock-full of information on what each specific comic publishing company is looking for in a writer/penciller/inker/colorist.
http://www.optimumwound.com/the-submission-guidelines-for-every-comic-and-manga-publisher-in-the-universe.htm

If you were interviewing for a regular nine-to-five job, you'd need to tailor your résumé to match what the job requirements are to make you seem like the most suitable candidate -- portfolio reviews are no different. If you're looking to get a job doing art chores for one of these companies (I'm looking at you, James), make sure your portfolio/submission shows that you can do the job they're looking for.

As I wrote before, the list hasn't been updated since a year before the DC relaunch set the comic industry on a bit of a boom again, so what each company may be looking for now could be different. Some publishers are missing from the list. I didn't see BOOM! Studios anywhere on the list and they've become quite an up-and-coming publisher of both licensed and creator-owned titles. Looking at the BOOM! Studio's website I found the following info on their submission process; apparently you can post art samples (not stories or scripts) to their message boards. They "do not reply to these posts directly, but have hired several people that way." Info on that here: http://forums.boom-studios.com/viewtopic.php?f=5&t=4

Not all these options are necessarily work-for-hire or freelance opportunities; Image Comics is entirely creator-owned comics -- basically you bring your comic, story pitch, script, and art samples to them and they'll help you publish it (at a cost to you, of course.) But this model has worked for people -- look at Robert Kirkman, Tony Moore & Charlie Adlard's The Walking Dead, Brian Michael Bendis & Mike Avon Oeming's Powers, or John Layman and Rob Guillory's Chew as a few hugely successful comics from Image.

Lastly, and most exciting for me, is the emergence of Kickstarter as a means to not just financing a project you're working on but also as a grass-roots way to find an audience. A lot of the comics projects posted on KS look like junk (bad design abounds!), but should you present your idea well you can find a following while maintaining complete creative control and ownership over your property. It's all do-it-yourself: you need to find a printer to print your story, organize shipping of the books once their complete, etc, etc. But isn't that the most exciting prospect?

Well, that's enough rambling from me. Hope some/all of you find this useful -- if not now, maybe at some point down the road.