Great food (at prices that students might actually be able to afford):
http://bistro1.co.uk/
A (free) museum which I visited last year just to kill a bit of time, but I ended up spending several hours there:
http://www.museumoflondon.org.uk/Docklands/
A really good Wetherspoon's pub, right next door to the museum above:
http://www.jdwetherspoon.co.uk/home/pubs/the-ledger-building
Crossing the Thames by cable car is fun (and inexpensive):
http://www.emiratesairline.co.uk/
and
http://www.tfl.gov.uk/modalpages/23863.aspx
A free (and very interesting) exhibition about the future development of the world's cities, right next to the northern end of the cable car:
http://www.siemens.co.uk/pool/about_us/cities/thecrystalbrochure.pdf
(There's quite a lot of interactive stuff; it's not 'dry and boring', honestly! They also serve great coffee there)