While I don't use it daily, I built https://collabuml.com https://collabuml.com (launched on HN a month ago: https://news.ycombinator.com/item?id=22955971 https

While I don't use it daily, I built https://collabuml.com https://collabuml.com (launched on HN a month ago: https://news.ycombinator.com/item?id=22955971 https://news.ycombinator.com/item?id=22955971) which has been helpful for me, I made it this way as lots of time you mostly care about writing system diagrams instead of freestyle whiteboard.