Main use: Display player/character name, control sound levels
The Hangout Toolbox has an obvious use: you can display your name (this is called Lower Third). This can be your Characters name, or your real name, or something else. You can also choose a nice color. There is also an option to add an avatar, which will be displayed beside your name. Below this there is the option for a full screen Custom Overlay. Use a 1024x576 transparent PNG, and you can add some nice borders to your video.
The other tabs of the Toolbox allow you to control sound levels, add scaling/moving overlays to your head or stream text into your toolbox (for example Youtube Comments).
Main use: roll dice, keep counters, add text labels
Dice Stream is one of the many dice rollers available. It is the most flexible one, so it is used fairly often. The main use is to roll dice. You can add them with the plus and then click roll to roll those dice. The results will show up in your video and in the Dice Stream sidebar. There you can click single rolled dice to mark them in various ways (circle, hex, crossed out, none). The mark will cycle with each click. This is pretty useful for systems where you roll dice pools and then select results (Cortex Plus).
There is also a Counter that you can use in various ways: Hitpoints, Plot Points, Fate Points. Make sure to choose a color that is different than the background!
The Text tab lets you add text to your video. This will show up in the left lower side of your video, right above the Lower Third Text. Here again the color should be distinguishable from the background. You can later edit the texts or delete them. Use them for Aspects, Assets, Complications or just for extra counters
The Lower Third tab is the same as the Google Toolbox Lower Third. Toolbox looks nicer, so rather use this.
The Settings tab allows you to choose colors for the dice markers and the change the behavior of the roller: should it keep dice and append, or should each roll be a fresh one? This depends on your game. For Fate or Pathfinder you rather want fresh rolls, so uncheck append. For Cortex Plus you like to add dice to your roll, so check append.
Main use: Display maps, keep notes, show handouts
Google Drive is an easy way to add handouts and maps to your game. You can also add a document where players can keep their collaborative notes. Be sure to tell the players that there is an undo option. One wrong click can mess up your map easily!
GM Tip: if you have two monitors, open your docs in a big browser window, not in the hangout. You will need the space!
On Air Tip: share your docs readonly to the Event. This lets viewer watch the documents while you are playing.