I need a cross platform screen sharing solution for a presentation. Users might have Windows, Mac or Linux... I've successfully hosted before with Yugma, but after upgrading to 10.10 I can't get it to work on my main box. I would potentially use TeamViewer, but the "Presentation" mode doesn't work with Ubuntu as the host. Anyone have other suggestions?
You can use VNC, for example tightvnc offers exactly that, with view only (and remote access with separate password) mode.
Unfortunately, with tightvnc you can't share your current desktop. You can use x11vnc (sudo apt-get install x11vnc) to share your current desktop. For example tightvnc client is good for connecting from Mac OS X / Linux / Windows to any VNC server (including x11vnc and tightvnc).