I had started with using MS Visio at my job. Though I had absolutely no experience in making diagrams, Visio was quite easy to get started and become comfortab

I had started with using MS Visio at my job. Though I had absolutely no experience in making diagrams, Visio was quite easy to get started and become comfortable in quick time. The downside of course is that it is not free. I would also like to know open source alternatives to MS Visio. I can see that Ubuntu 12.04 comes with Libre Draw, but I haven't tried it yet.