Create a new discussion or document and attach files. Note: this only works for 5 or less files. This is a great way for one person to share resources and have a comments or discussion for feedback and suggestions.
In a group, the group owner can create categories. The categories can be titled by subject, by name, etc. and when users upload files - they can then tag them with the appropriate category. The users can then search the discussions and documents by that category- and it will show all things that are tagged and associated with that category.