First, we need to create the script that IE will run when our option is clicked on the context menu. This script is nothing more then an html page. Here's the code I used:
//Sends a media URL to XBMC for playback
//Replace the xboxip value with the IP address of your xbox running XBMC
var parentwin = external.menuArguments; var doc = parentwin.document;
var xboxip = "192.168.1.127";
var element = doc.activeElement;
newwin = new ActiveXObject("MS.XMLHTTP");
newwin.open("GET", "http://" + xboxip + "/xbmcCmds/xbmcHttp?command=playfile¶meter=" + element.href, 0);
Save the document to a location that you'll remember like, C:\xbmc.htm.
Now we need to add our entries to the Windows registry so it'll show up in IE so fire up regedit. Make sure the following key exists in your Windows registry. If it doesn't, create it.
Make a new subkey and name it whatever you want the text of the context menu entry to be. Mine, for example, is Send To XBMC.
Change the value of the (Default) entry in the right hand pane of the key you just created, to point to the location of the file you created in step one. For example...
Create a new binary value under the default entry and name it Contexts. Change the value to 20, which will make it only show up when a link is right clicked.
Close regedit and fire up IE to test it out. When you find a link to a video, right click it and you should have a menu entry like Send To XBMC. Click it and once it buffers, the video should start playing on your xbox. If anyone get's any use out of this or makes it better, I'd like to hear about it!