Simplest is to create a XAML browser applications (XBAPs) (
http://msdn.microsoft.com/en-us/library/aa970060%28v=vs.110%29.aspx[
^]).
In Web applications there are lot of possibilities. In you have already WPF applictaion, you can go for Silverlight (
http://www.microsoft.com/silverlight/[
^]), so that you can use almost 80% of your existing code base.
Further if you want more reachability then try ASP.NET MVC, Web Form etc.
It is strategic question and answer depends upon various factors of current and future perspective.