Sometimes I just miss seeing an OSD message on my PC and there's no way to see what it was (unless I'm logging xPL messages). That inconvenience served as the inspiration for OSDBuffer, my second C# application. OSDBuffer is a typical OSD popup application, however, it buffers the last 10 OSD messages received. You can scroll through them when you want. You can also customize the frame around the popup to your liking. Here's a video of it in action.
Read more about it & download it from here.