One of my main use cases for Matrix is when I need to manage a non-finite list of things related to an entry (e.g. translation links for articles may trickle in over time, and there's no pre-defined list of sources of them).
Sometimes Matrix feels like overkill, so I'm wondering what other folks use for this purpose.
Someone mentioned Pixel & Tonic's List, which is a good one for my translation links use case; it's available in their Dive Bar: http://pixelandtonic.com/divebar
Another common use case is images: how do you allow users to add a non-finite set of images to an entry?