Broad request, here's my 2¢
For Hardware protection, data loss prevention.
External HDD for Time Machine (I like the Lacie Rugged drives)
Protective Case/Sleeve/Bag (I like Tom Bihn and Chrome)
A laptop stand (get it off the desk to significantly reduce the risk of drink spill damage)
An online backup account from Mozy/Carbonite/Backblaze (Happiness is multiple backups)
A Dropbox account for schoolwork (laptop stolen/broken night before term paper is due? No worries, I can go to the computer lab and pick up right where I left off)
An Evernote account for schoolwork (clip references, organize courses into notebooks, record lectures, etc)
'Reward for return' Identity Labels (I use stuffbak's metal labels)
Labelmaker (Label all your accessories and chargers with your first name and phone number- if it's worth more than 75$ or so, use a stuffbak type label instead).
An iTunes account with 'find my mac' enabled
A 'Prey' account as a backup to 'find my mac'
Extras:
External Monitor w/ MDP and built in speakers (HDMI too and it can double as a game console screen if you are bringing a gaming device or Bluray player; built in speakers reduces cable spaghetti) (check newegg, amazon for best deals)
External non-apple mouse for gaming (Razer FTW

)
External mac Keyboard (so laptop is easy to type on when on its stand at your desk)
A USB Ethernet Adapter- wifi may be nearly ubiquitous, but it's nice to have a backup ready.
USB headset- for Skype/ video chat/ gaming.