So, in light of recent tumblr events, a statement:
If you want to save a copy of any of my fics to your hard drive - YES, GO AHEAD. (I have something like half a gigabyte of fanfic saved to my hard drive myself.)
If you want to print a copy of any of my fics out and keep it in a three-ring binder somewhere - YES, GO AHEAD.
If you want to lend the three-ring binder to every person in your English class/office/college dorm - YES, GO AHEAD.
If you want to turn a copy of any of my fics into an ebook and put it on your nook/kindle/iPad/etc. - YES, GO AHEAD (AO3 very conveniently lets you do this automatically)
If you want to email the ebook to all forty-three of your closest friends - YES, GO AHEAD (or just point them to AO3 and tell them to click the nice "download as epub" button themselves)
If you want to publish copies of said fic as zines and sell them for $$$? ASK FIRST
I will probably say yes provided you're doing it as a for-cost zine instead of for a profit and aren't doing something likely to get all of us sued by Marvel/Disney, like publically listing it for sale on Amazon or Lulu, but still, please ask. If nothing else, I might have a clean, all-in-one-word-document file of the fic to make your life easier. (Also, it's usually considered polite in zine-making circles to give contributors copies of the zine)
Actually, let me mention that sued by Marvel/Disney part again. Disney is infamous for the rabid psychotic intensity with which they defend their copyrights. Listing Avengers fanfic for sale on widely-used public sites like Lulu, Createspace, Smashwords, or, god forbid, Amazon, is probably a good way to risk facing a C&D letter if the wrong team of corporate lawyers somehow notice it.
Zines have been around in fandom since long before the invention of the internet, and there's a whole culture and etiquette
surrounding them, some of which is probably just us old school, pre-tumblr fans being fuddy-duddies, but some of which exists for a reason. Selling printed fic at cost and not making a profit is a fandom etiquette thing that corporate lawyers probably aren't going to distinguish from selling it to make money, so it's a good idea to try and stay under the radar. And, again, to ask the authors first, because while most of us will say yes, some fans are very, very sensitive about having complete control of their fic and will not only say no if asked, but be extremely upset if you go ahead and distribute it anyway.
(You know those artists who are so upset at having a piece of fanart reblogged on tumblr that they don't feel comfortable posting art at all anymore and delete their entire pixiv or deviant art account? That reaction is not unique to artists; some writers feel that way, as well)ETA:
And if it's co-written? (Which means pretty much all of my longer Marvel fics) Please, please ask seanchai
as well before openly distributing any kind of printed zine. Just because my stance on fic is "Yes, go ahead, podfic it! Translate it! Save copies! Print it out and tape it to the walls of subway cars!" doesn't automatically mean that her response will be the same.