The videochat game is dominated by three major players. Skype is still, far and away, the most popular, but seems to have stalled a bit since its acquisition by Microsoft. Google Hangouts has a nearly unstoppable amount of momentum right now, and even wants to get into the Enterprise game, but it comes with a lot of bells and whistles. Apple's Facetime is ubiquitous across Apple's own devices, but it's limited to those platforms.
If you just want to open a browser and start a quick-and-dirty videochat, you don't have many options. Tinychat used to be the frontrunner, but it's getting weird lately. Appear.in wants to step in and fill the hole.
Appear.in works without a login, a plugin, or any other extraneous features, because it runs on a technology called WebRTC, which is baked into modern browsers like Chrome, Firefox, and Opera (which means that, currently, those are the only browsers capable of running Appear.in).
To use the app, just open the site in your browser, name the room, and give the app permission to access your webcam.
Once you enter the room, you have a few options. First, add up to 7 people to the chat by simply copying the link and sharing it with others, via whatever platform you choose (email, Twitter, etc.). You can disable your mic or camera by hovering over the video window, lock the room so no one else can enter, go fullscreen, or chat with other members of the chat with a popup chat window at the bottom of the screen. You can even add a custom background image to the room.
The room also stays available, so everyone in the group can bookmark it and use it as a permanent virtual conference room of sorts (if you lock the room, you'll have to fork over an email address to enter it and unlock it in the future, from what I can tell).
If there's a simpler way to videochat from a PC, I'm not aware of it. Video quality is good, no downloads are required, and it works in most major browsers. Appear.in does what it sets out to do, which is making videochat as simple and stress-free as possible.