The post below this one is almost the same but I'm looking for it on the viewable side of things. Sorry if it seems like I didn't research and just posted - I did look around.

- multiple groups per user are not possible yet
- blogs cannot be hidden from users by default, but you could write a simple plugin to deny access, if the user is not a member of a blog, but that would e.g. not hide the link to the blogs in the bloglist etc.

What would be my best resource for learning how to write that plugin. I'd like to give it a go and would be happy to share the plugin, but I'm not a programmer but can play around with code.

See http://manual.b2evolution.net/CreatingPlugin

Also http://doc.b2evolution.net/ is helpful. Especially http://doc.b2evolution.net/v-1-8/plugins/Plugin.html for the Plugin API.

Good luck :)