Does anybody know of any pre-canned gadget/widget management framework (along the lines of iGoogle etc) that I would be able to use on an ASP.NET MVC site (presumably loading divs via jQuery etc)?
In particular, I'd rather not write all the selection / location code if there is something decent already available. (I would expect to write the actual widgets / content etc myself...)
I was waiting to see if you got an answer on this one as it's something I'm interested in too. As you haven't, I'll tell you what I know (it's probably not so useful but it might get you started...)
I've used something based on the ExtJS portal demo in a previous project - there are some license costs involved depending on the deployment scenario though, and besides, it turned out to be quite slow and cumbersome, and rather tricky to customise - the default for the ext toolset is for the ui to be built entirely from javascript, not from markup, and while it was possible to coerce it into working on top of existing markup, it seemed more difficult than it needed to be. That aside, it worked well in the end, and with the paid version the support is very good.
I've also implemented a widget / portal screen based on jquery-ui sortable which worked really well - the basic implementation was very quick and easy but writing the code to save and load portal settings took more time than I would have liked.
If I were doing a similar project now, I think I'd evaluate this instead - it looks ok from a cursory glance and it's open source - it's built with jquery-ui sortable, so the core should be solid enough, and the slightly uneven animations on the demo version should be easy to sort out assuming it uses the standard jquery-ui sortable options. It has functionality to load/save portal settings too by the looks of it, so it should mean less hand coding that side of things.
I have used Telerik RadDock in the past and found it to be pretty good. It renders in divs and is relatively easy to style.
It doesn't cost too much if you are using it commercially.
http://demos.telerik.com/aspnet-ajax/dock/examples/overview/defaultcs.aspx
http://net.tutsplus.com/tutorials/javascript-ajax/inettuts/
This guy put together a great tutorial on implementing a iGoogle like drag/drop widget interface. Even links to a working example.