This website provides challenges where students have to replicate specific 2D images on a 3D platform. For the spatially challenged, such as myself, this is not as simple of a task as it first seems! I particularly love this site because it easily lends itself to small-group collaboration, trial and error discussions and problem solving -- all skills for our 21st century learners. Put it on the SMART Board, and work through together as a class, or make the SMART Board a 'center' with this one Geometry activity for one group of 3-5 students to tackle, while other small groups work on additional geometry challenges around the room (traditional pen and paper Math problems, building 3D models, etc.)
The British Library has released 1000 books from its 19th Century collection into a free iPad app that includes novels, historical works, poetry, philosophy and scientific books.
The books have been scanned in high resolution and color so you can see the engraved illustrations, the beauty of the embossed covers, along with maps and even the texture of the paper the books were printed on.