The publishing world has changed dramatically in the twenty years since I first took any serious interest in it. That shouldn't be surprising; lots of "worlds" have changed dramatically in that time but I've had reason to think some about those changes recently.
That first period of taking writing seriously would have been in the very early '90s. Most of what I tried to write then (as now) was genre fiction, almost entirely SF/F/H. I was also working completely in the short fiction world. There were a handful of "big" magazines (Analog, Asimov's, F&SF being the biggest) and a lot of small press magazines which paid anywhere from a few cents a word to not a cent. Those small press magazines also tended to come and go with some regularity. There were occasional themed original anthologies which took unsolicited submissions.
Though I didn't attempt anything novel-length at that time, I was aware of the fact that there were Publishers (big and small) and Vanity Presses/self-publishing. The general impression I got was that no one who seriously considered being a potential professional Writer would be going the self-published/Vanity Press route.
Fast-forward to 2011 and some things look the same, others look a lot different. In the short-fiction world, most of the "big" magazines of 1991 are still around, though circulation numbers continue to drop and F&SF switched to bi-monthly larger-size issues a while back. Small press magazines still exist, but a large percentage of them are electronic.
In terms of electronic publication, the huge change has been the rise of the e-reader and eBooks. No longer does self-publishing necessarily mean throwing a bunch of money at someone to print copies of your books and then hope you can sell them so you aren't losing money on the deal. Sites like Smashwords and Amazon's Kindle Direct Publishing have been game-changers; you upload your "book" (which could be non-fiction, a novel, or even a single short story) in the proper format and its made available in their marketplace. When people buy it, you get a (typically hefty) percentage of the sale price.
Now, the trick of course is that people have to buy it. Otherwise, you've burned your first publication rights and haven't gotten paid for it. Still, I suspect in the Twitter/Facebook/Google+ world, it's a lot easier to drum up interest in a book by someone nobody has ever heard of than it was 20 years ago if you were driving around on a tour of independent bookstores with a couple crates of books in the back of a van. John Locke has sold over a million books that way, and even with the reduced percentage of the sale price he's received by pricing his books at 99 cents, that still represents a lot more money than many authors ever make. Obviously one example doesn't mean "Oh my gosh, everyone should be self publishing novels at 99 cents -- it's a gold rush!"
For me at least, there's still something ephemeral-feeling about eBooks. If you publish an eBook, even one that sells well, you can't give signed copies to your friends and your grandchildren won't one day run across a copy in a used bookstore or library.
But it does give one reason to think, especially since we're still clearly in the dawn of the eBook age. Being flexible and keeping your eyes open for changes will be valuable skills for writers new and old.