Wonderfl is described as 'wonderfl is a service where you can build Flash(swf) online'. There are seven alternatives to Wonderfl, not only websites but also apps for Windows, Linux and Mac. The best alternative is Scratch, which is both free and Open Source. Other great sites and apps similar to Wonderfl are FlashDevelop (Free, Open Source), KoolMoves (Paid), Artist Code (Paid) and Express Animate (Free).
Artist Code is an intuitive software for creating animation ( Movie, Animated Gif, Images) only by coding, it allows you to add image, text and pixels and place them with simple script offering you a fun and unlimited way to create whatever you want.
Express Animate is free animation software that gives you the ability to animate shapes, text and imported images. You are also able to enhance your movie projects in post-production using key-frame motion animation, masking, dummy objects and more.
Create Flash websites, slide-shows, banners and other animations. Import photos, screenshots, Flash cliparts, animated GIFs and video files. Add shapes, lines, curves, text, 3D effects and gradients. Insert links to other pages, create buttons and clickable hotspots.