Ask HN: Flow chart tool for MS Office

Does anyone know of a simple FOSS tool to produce flow charts that are suitable for embedding in Microsoft Word and Excel documents? MS word smart art always seems like a real faff. Being from a finance background I sometimes turn to excel, but that leaves you with manually having to align the arrows. What solutions have other people found. I don't need strict UML/BPM or anything (although that wouldn't hurt to be in line with it), I am just trying to document short processes quickly and in a more professional looking way.