I like multicast events in Microsoft .NET. Basically, a single event property (using Delphi terms) can be linked to multiple event handlers (as opposed to standard Delphi's events which can only be linked to a single event handler at most). In Delphi 7, a multicast technique is already used internally in TApplicationEvents, AppEvnts unit. In this case, the result is that you can have multiple TApplicationEvents components in your project (perhaps on different forms), each of which can receive and handle events coming from the global Application component.
It seems that some research is being done of multicast events support for future versions of Delphi for Win32.
In one of my projects, I've been experimenting with my own implementation (just for my own, non-visual classes, without any designtime support). It seems to be a success and I believe it helped me write cleaner, more modularized code. Writing it was fun, too.