Stock & Resources
I see Stock & Resources as a category of art on deviantART where the entire focus is on helping others and providing them with what they need. This helps artists of any medium! Photomanipulators for example rely heavily on the stock photos they find here. If you draw or paint, digitally or traditionally, many stock photos can be hugely helpful as reference, as can line art and textures. There's literature templates, fonts, fractal and vector resources, designs & patterns for artisans and crafters.. and then there's tutorials for any kind of art, and about deviantART itself.
So one great way to contribute something to the community and your fellow artists is to provide such resources!
We will not go into this in depth as it has its own Community Volunteers and Project Educate weeks that should help you get started! 
Informative articles:
- An Introduction to the Stock & Resources Category (note, a few years old)
- What is stock? by StockProject
- Welcome to Resources Pack - everything you need to get started with stock & resources.
- Do's and Don'ts of Stock Photography
- A few helpful Stock related resources from `UnicornReality
Other handy links:
- Browse Stock & Resources category
- Most recent Project Educate
- The current Community Volunteers at the time of writing: Elandria & PirateLotus-Stock
- If you're reading this long after it was posted it's possible there are new CVs, you can always look up the current ones on The Community Relations Team.
deviantART Related
The deviantART Related category is like Stock & Resources in that it's a varied category with a common theme - but in this case, deviantART. While perhaps best known for deviantIDs, it also contains Journal and Gallery Skins, stamps, user scripts and styles et cetera. For you, as deviant with the wish to contribute to the community, some of those are of particular interest, some not so much - so let's have a look into some of them shall we?
Again these have had their own Project Educate (and other) articles about them, that we will link for each category!
- Deviant Stamps - many deviants love to include stamps in their journals or on their pages or artist's comments, sometimes silly, sometimes to communicate important messages.
- Journal & Gallery CSS - know some HTML & CSS? Use these skills to decorate your own gallery folders and journal, and publish your skin for others to use while you're at it.
- Browser Scripts & User Styles enhance the way deviantART looks, and works! Styles can change the appearance while scripts can change - normally, add - a wide range of functionality to deviantART. These are normally done in CSS or Javascript. For some great examples of scripts see Did You Know? Browser Scripts.
- deviantART Suggestions, visual or written, help you communicate your ideas for deviantART. They can not only spark discussion with other deviants about improvement of the site, they will also be seen by the deviantART staff and a good number of these have been implemented in the past.
- Also see the "dA Suggestions Bible" aka A Guide To Creating A Suggestion for DeviantART.
Other handy links:
- Browse deviantART Related
- The current Community Volunteers at the time of writing: bradleysays
- Again, if this has changed see The Community Relations Team.
Try your hand at some of these and have fun!
dA suggestions Bible. 