I\'d love to know if there is such a thing as a Gecko.NET ;) I mean, just like we can embed a WebView and that is an \"instance\" of IE7 inside any Windows Forms application
I'd just like to point out, to all looking to embed Gecko into their applications, that the GeckoFX project appears to have been abandoned by its creators (Skybound Software). MozNET, while previously based on GeckoFX, sorta' picked up the ball and ran with it. It has the full ability to print, do print previews and allows you to set it all up via the native Windows print dialog, even - and a whole lot more.
Additionally, if you find yourself using Gtk instead of Windows.Forms, there is a tarball of webkit-sharp available that allows for easy embedding of WebViews into Gtk# applications.
It certainly is possible. All you need to do is register the Mozilla ActiveX control (mozctlx.dll I believe), and you can drag it onto your form as any ActiveX control. The programming interface is similar (though not identical) to the IE one, and you can even use the Microsoft.MSHTML.dll managed library for control in some cases.
I believe this is packaged with Firefox. If not, you can get just the embeddable bits from Mozilla as well. Just do a Google search for Mozilla ActiveX control or Mozilla Embedding C# and that should take you down the right path.
As of October 30, 2011, there is new information to add since the time of the previous posts. Specifically, while Skybound stopped maintaining their version, there is at least one actively maintained, free, open-source fork available.
I'm using Hindle's fork at BitBucket, which, by virtue of his tool which parses XpCom idls and creates c# wrappers, is rapidly updated with support for each new version of Firefox/Gecko.
See this post for an overview of other choices.