One of the leading competitors in the RIA space is the Adobe Flash Platform. The platform is composed of a number of tools and technologies designed to provide rich and compelling user experiences while maximizing developer productivity and designer involvement.
By targeting Flash Player, developers could also break away from browser and platform incompatibilities. One of the many nice features of Flash Player was that content and applications developed for any particular version of Flash Player would usually run on any platform/browser that supported that version. With very few exceptions, that remains true today.
To find a tutorial of using Flash Builder 4.5 click here.
You may review blog articles on Flash Builder here.