Something great happens when a bunch of my students bring their iPads to the classroom. Individual work groups start looking things up on the Internet during tasks, bulky laptops and their power cables are left in bags, more notes get taken in lectures and posted immediately to our shared Minigroup spaces. I've walked around the room capturing student sketches with the iPad camera, then hooked up to the projector to share them with the whole class.
It's worked very well. I've switched entirely to the iPad for my own lecture presentations now, but there's still one thing I want to get rid of entirely: The VGA cable. The need to plug the iPad into an always-too-short-and-inconveniently-positioned cable in order to present has become the remaining limiting factor for most of my classes. The iPad's battery life and portability (especially with the iPad mini) mean that I'm no longer tied to the chained-down iMac at the front of the room. I can walk around, read my notes, talk to students, look things up on the Internet—but the ubiquitous VGA connection to the projector remains an anchor on everything we do.
There's an obvious and simple solution to this problem, and though it's not generally marketed as classroom technology it's a super product that's affordable and fairly straightforward to implement, with a couple of caveats. Apple TV was initially released in 2007 as a hard-disk-based but Mac mini-sized iPod equivalent at $300 that connected to a TV set and let you watch your movies and play music through your home entertainment setup. Since then it's remained a "hobby" for Apple, but it's shrunk to the size of a hockey puck, lost all of its moving parts (it's now flash-memory based), and costs a third of the launch price. It now connects to a TV via HDMI, runs 1080p video, and streams your purchases directly from the iTunes Store without syncing.
The killer-classroom-feature though is Airplay–Apple's video-over-wifi system that lets you send the screen of your iPad (and specific content from other iOS apps) to a connected HDTV, or HDMI-equipped projector. Since many modern classroom projectors have the necessary port it should be easy to hook up the tiny Apple TV box and then be free to walk around your classroom, presenting as you go. I say should though: While many of the classrooms in which I teach have HD projectors, IT-departments have seen fit to save money by not hooking up the necessary cabling, and we're stuck with VGA. Until that changes I'm keeping my own HDMI cable handy, and lobbying those in a position to do something about it.