Students use 21st century technology outside the classroom so why not inside the classroom as well? Here are a handful of apps that can be useful in the classroom as well as preparing for classes.

Penultimate
Penultimate gives you a quick and easy way to take notes, sketch, and markup an existing graphic/image on your iPad. Save your work to organizable notebooks, send via email or integrate with your Dropbox or Evernote accounts. They also offer several types of papers to write on like graph, lined and plain.
More information about Penultimate

Evernote
From voice memos to snapshots to basic notes, Evernote gives you everything you need to stay organized. Your content can be organized in notebooks and is fully taggable which makes searching simple. Storage is handled in the cloud so your content is available from anywhere. Available for mobile, tablet, Mac OS, Windows, Firefox, Chrome and just about any other platform.
More information about Evernote

CloudOn
Edit, create and manage your Microsoft Office Word, Excel and PowerPoint documents in this easy to use iPad app. The interface has been recently tweaked to be more tablet friendly and is just like working in the MS suite. CloudOn integrates with your Google Drive, Dropbox or Box.net accounts. Best of all, it’s free!
More information about CloudOn

Keynote
Leave your laptop in your office! Keynote allows you to import existing PowerPoint presentations or create new ones right from your iPad. Display your presentation wirelessly using and Apple TV and Airplay or plug right in using an adapter.
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eClicker
This is actually two apps. The instructor uses the eClicker host app to enter questions and begin polling. The students can either use the free eClicker client app for iOS or simply type the host’s address into any web browser. This simple system provides instructors real-time feedback and is a great way to evaluate learning in the classroom. Currently only available for Apple devices.
More information about eClicker

These are just a handful of helpful apps, which apps are you using in the classroom?