<p>I'm developing a .NET 3.5 XBAP application that runs perfectly fine in FF3 and IE6/7 etc. I'm just wondering if its possible to get these to run under other browsers, specifically (as its in the limelight at the moment) Google Chrome.</p>

At the moment, XBAPs do not work in Google Chrome.  I've gotten it to run once, somehow, but every time there after I've received an error that the browser cannot locate xpcom.dll.  Apparently this error occurs for more than just XBAP applications.  From what I've read users will have to wait for a fix seeing as Chrome is still in beta.
Update:
Looks like it's not going to be fixed:
http://code.google.com/p/chromium/issues/detail?id=4051