What do publishers provide to authors in different disciplines? Discussions about academic publication (for example, the recent Elsevier boycott, the actual cost of publication, open-access initiatives by universities and funding agencies, citation cartels, or post-publication review) are often muddled by the fact that publication practices and culture vary significantly from one discipline to the next.  I would like to see some of these differences explicitly teased apart.

I'm particularly interested in exactly how publishers in different disciplines help move authors' ideas to formally published papers.  Publishing in any discipline requires the combined effort of authors, publishers, editors, and reviewers, but the distribution of these efforts (and their associated costs) seems to vary from one discipline to the next.

What specific services do publishers provide to authors in your discipline? Please only one answer per discipline.  (If necessary, define "discipline" as "set of researchers with the same publication practices".)

(At a deeper level, I am curious why so many people seem to associate the value, authority, and prestige of various publication venues with their publishers instead of their authors, editors, and readers.  But that's not a good question for StackExchange; let's stick to the narrower factual question.)

I'll provide an answer for my own discipline.
In theoretical computer science:


Papers are written, illustrated, and typeset (in LaTeX) by authors and refereed by unpaid volunteers.  Some publishers give free journal subscriptions to editorial board members; a few pay a small stipend to the editors-in-chief of each journal; otherwise, editors are also unpaid volunteers.
Most journal publishers provide an online system to help editors track submissions and communicate with referees.  Conference publishers do not; most program committees use free systems like EasyChair or HotCRP.
Some journal publishers employ copy editors, who produce the final camera-ready paper directly from author-provided LaTeX and image files.  Specifically, copy editors correct (and invariably insert) spelling and grammar errors, and reformat the paper (especially the bibliography) to fit the publisher's standards.  For other journals and most conference proceedings (Springer's LNCS series being a notable exception), copy editors simply do not exist; camera-ready papers are produced by authors using publisher-provided LaTeX packages, except possibly for page numbers.
Most publishers provide electronic versions of their papers to subscribers.  Some publishers also provide extensive indexing and cross-referencing of their publication catalog.  Online-only venues are still relatively rare, so for most venues, publishers print, bind, and ship paper copies.