WordPress Multisite - Structure sites into categories?

Question

Store sites into categories

When using WordPress with multisite (like the old WPMU) for very many sites, it would be nice to store them into categories. Site categories that is, not post categories.

Site meta / custom fields

Maybe there is a way to use some kind of meta / custom fields for sites? Is there? How?

Plugin or example

A plugin would be nice, or an example of a start, what hooks / functions to use.

Answer 1

Answering to this Question, Multisite: How to add Custom Blog Options to new blog setup form?, I ended up doing a plugin that does exactly that: adds a blog meta field to give each site a Category.

It's a simple meta field, meaning: no category tree. I just revised the code and updated. Available in GitHub.

Main hooks:

• add_signup_meta
• signup_blogform
• wpmu_new_blog