A product launch just isn't the same without digging through some source code to see what goodies are hidden under the hood. It seems like most new Google products have code hanging around that doesn't seem to do anything (yet).

Google Notebook isn't any different — there are several references to interesting things that I'm sure you will enjoy. These should not be considered a guarantee of future functionality — but I would say they are a pretty good indication.

The first piece of code is quite obviously "experimental" since it explicitly says so. This code definitely indicates they are at least testing "gadgets" in Notebook. I'm not sure how gadgets will enhance the service, but I guess they have determined it would be useful at some level. By the look of it, you will be able to use Google created gadgets along with third party ones from the IGoogle directory.

ne_s.prototype.yJ=function(){
this.xm("Add a Gadget [Experimental]");
this.Tt("Add Gadget >>");
this.zB()
}

ne_s.prototype.lJ=function(){
this.Tt("OK");
if(this.Wh){
this.xm("Setup Gadget");
this.BB()
} else {
this.xm("Loading gadget information…");
this.au(this.qa["url"])
}
}
…
ne_e.innerHTML="These are the same kinds of gadgets that you can add to your Google Personalized Homepage.";

The second piece of code that I thought was interesting is the reference to image uploading and editing HTML. Currently you don't have a lot of control over the final appearance of your notebooks — you are pretty much limited to pasting stuff, changing the font and creating links. If this code is any indication, it could soon more closely resemble Google Page Creator.

var ne_d = ne_u.setupUpload (this.yourImagesTab, "Upload an image", ne_, this.bE.bind(this), ne_c, ne_b, !this.ag.Qa(), this.mK);
…
var ne_ = ne_aa.createTabDiv(ne_4.HTML_ID, "HTML", "Edit your HTML here", this.c, this.xa.bind(this));

And the third interesting snippet is for a debug window that according to the code, you have to hit 'D' inside the main "caribou" window to stop debugging. What is caribou though? Caribou was the codename for Gmail before it was released. Could this mean some kind of Gmail integration in the future? The interface already resembles Gmail wouldn't you say?

var ne_ = "To turn off this debugging window,hit 'D' inside the main caribou window, then close this window.
";