We will probably see a bunch of these over time whether they are better or worst than OnLive we will see. GaiKai seems to be a new cloud gaming service that has sprung up.  GaiKai lets you play any game from within your browser. No files, no installation, just a browser it claims. Video and audio automatically adapts with your bandwidth from ~500Kb/s to ~2Mb/s. GaiKai also claims any game can be played without modificiations.

More details to come.

You can sign up for the GaiKai beta here.