Ability to categorise spaces as you create them

I was wondering what would be the best way of building a menu of the existing spaces based on their labels?
I saw that some expensive plugins provide themes with horizontal navigation bars based on space labels and I was wondering whether a similar functionality could be achieved within a "home space" (used as landing page) with some macros, or whether it requires any theming, or writing plugins.

Practical example:

I have

• space "Project 1" with label: projects
• space "Project 2" with label: projects
• space "Java best practices" with label: documentation
• space "JIRA documentation" with label: documentation

And I would like somehow to list (regardless of the layout)

• projects
  • Project 1
  • Project 2
• documentation
  • Java best practices
  • JIRA documentation

Of course I don't expect a horizontal navbar without doing some theming, but at least being able to create a space that I would call "Home" (and set it as landing page for Confluence) in which I can build some blocks of spaces based on their labels.