Music

There are loads of great Apps. A good starting point is GarageBand
Vjay is a lot of fun for mixing sound to video

Video and Media

iMovie works well but Avid is worth a try as is TouchEdit.
There are a myriad of blogging apps and Newsfeeders
YouTube is ready installed and the Vimeo App is a free download.
Newspapers and magazines really work on e iPad
There are some great Stop Animation movie apps out there. IMotion HD is well reviewed and free.
TouchEdit let's you work with a pro workflow on your iPad. Quite an exciting app.

Art

This seems to be a useful link:
iPad in an Art lesson apps
SketchPro is good as are Brushes and Inspire
Here's what can be done on an iPad:Check out this link
Dont forget the instant access to galleries that a student with an iPad will have.

Photography

There are apps which link to Flickr etc Guardian Eyewitness has some amazing photos.
iPhoto is a paid download but Photoshop and Snapseed are both free photo editors.

Drama

The Shakespeare App is free but the camera is obviously ideal for recording and analysing work. Video/audio evaluations and photo to support the written coursework. VR could also support the written element. Apps like Notability can be used to develop multi media coursework portfolios. Other Apps worth considering;
MoodBoard for design / staging
Storyboard for plot
Scribbeo for annotating video
iTheatre is a useful What's on app
There are a number of promising apps, such as StageWrite, that fail to deliver.
Digital Theatre have an app that allows you to store and watch productions on your iPad
The V&A have several apps including a 100 plays of modern british theatre.