What happens after my paper is accepted? Today I was informed by a journal that my paper was accepted.  So am I done with it, i.e. is my input no longer needed? Do I just sit back and wait for it appear?
After your paper is accepted, it is passed to the publisher's production department. They'll do things like copyedit it, typeset it, proofread it, organize the references, and so on.

Your involvement as an author isn't completely over. At some point in the production process, the publisher will show you proofs (which is what the paper looks like after all of the above has been done). You get to make final changes at that point, e.g., the editor might have decided to accept your article with some minor comments still outstanding from the reviewer - now is the time to make those changes. It's also possible the copyeditor will have questions about the text; this is also the best time to address them.

Your involvement usually ends when you approve the proofs (very uncommonly, problems might be found even later in the production process that requires author input). After you've approved the proofs, you can sit back and wait for the paper to appear.