Anki's collaboration support is limited at the moment, but it is possible for multiple people to work on content together.
If you are creating cards that have no sounds or images, then the easiest option may be to take advantage of an online document collaboration service such as Google Drive.
With this system, you create your cards in a spreadsheet (one column per field in the note type you're using). To allow updating easily, the first column should be one that you do not expect to change if you update the cards. You can add and edit cards together at whatever time you want; when you're ready to update your collection with new and updated cards, each user can export the spreadsheet to a text file and import it into Anki .
If you are creating cards that contain images or sounds, it gets more complicated. You can use the above approach, but it means you'll need to distribute the media files separately. Instead, we recommend taking turns to create the content. For example, if students are collaborating on a class, student A creates a deck "lesson 1" and puts all the first lesson content in it, then student B creates "lesson 2", and so on. As each lesson is done, the student exports the deck to an apkg file, and uploads/emails/etc it, and the other people import it.
Using a separate deck for each unit of work makes it easier to export the content separately, instead of sharing everything that's been created so far (which would lead to large files). After other users import the content, they can move it to another deck if they wish, using the computer version.
Advanced users can skip the separate deck step by instead creating a filtered deck using something like 'added:7' to only include cards added in the last 7 days, and then exporting that filtered deck to share.