If you are looking for a lightweight editor to design WPF and silverlight application, or you have already done some job with XamlPad, then Kaxaml is the best tool for you.
It's shiped with a very nice UI with drag 'n' drop capabilities, intellisense and lots of other features that we find in Microsoft Expression Blen, and of course it's free.
for more information and downloads : http://www.kaxaml.com/
