The IYOPRO Process Modeler is SaS solution to model business processes over the internet. While several tools like this are avaliable, this one is especially interesting as it combines BPMN and Silverlight, a strong modeling standard and a powerful RIA technology. It looks and feels like a desktop application and is fun to play with.
In some areas it is limited (e.g. no export) but it is worth to try and see how it evolves in the future.
What I like is the capability to visually simulate processes and the timeline view. This can give you insights about the process flow at runtime.