After Skype closed their Skypecasting feature back in 2009, I searched extensively for another tool that would offer the same sort of tool. Skypecasts were sort of like ham radio combined with talk radio, and provided an excellent platform for evangelism.
My aunt recently told me about a tool called Zello that has features almost as good as the original Skypecasts. Strangely, Zello's main feature is a way to use your computer or mobile device as a simple walkie talkie. But they also have a "Channels" feature that is quite similar to Skypecast. And it's completely free for personal use.
My Zello handle is 'danielofaz'. Feel free to look me up.