WikiWeb [wikiwebapp.com], developed by Baltimore-based design startup Friends of the Web, is an alternative iPad or iPhone reader that provides a visual and interactive way to explore all knowledge as described at Wikipedia.
Be sure to watch the introductory movie, which is quite charming by itself.
The app's interface consists of 2 separate panes, one with a calm rendition of a Wikipedia article, the other with a weighed network graph of all connections of that article with any other article on Wikipedia. Interestingly, these network maps can be shared through email or Twitter.
As there already exist plenty of other Wikipedia readers on the market, the key differentiating feature is that of visualizing the connections, and using the resulting graph as an open-ended way to browse through more, and potentially unexpected, articles.