It's not exactly a Hypercard-alike, but have you take a look at Twine? http://twinery.org
The 2.0 version is a choose-your-own adventure generator that can go from simple (create 'pages', make one-way links between them) to complex (use CSS + Javascript to create multiple panes, keep track of variables, write graphics, etc), and it exports as a Tiddlywiki-based self-contained HTML file.
The 2.0 version is a choose-your-own adventure generator that can go from simple (create 'pages', make one-way links between them) to complex (use CSS + Javascript to create multiple panes, keep track of variables, write graphics, etc), and it exports as a Tiddlywiki-based self-contained HTML file.