Google Drive's Presentation may not be the most famous slideshow creator (Powerpoint wins that award), but it's free and relatively robust. Now it has become slightly easier to use with the addition of Chromecast support.
The feature has been tested quietly with a few users for a while, but is now live for everyone. From the web, you can click "Present" drop down and choose "Present on another device" which will include the option for any Chromecasts connected to the network. The only thing left to do (apart from importing a Chromecast) is to convince your boss that connecting a dongle to the conference room projector is easier than dragging in a laptop. Shouldn't be that hard a sell.