We are hoping to settle close to the University. I think S2 and S11 were some of the areas that we were looking at.
I've briefly browsed the Sheffield Forum. I better look over it more closely now 
quick rundown of where to live in sheffield close to the university-
S1- city centre flats. usually more expensive than equivalent houses in the suburbs.
S2-Highfield/lowfield (london/queens road) is okay if you really want to be as close as possible to the city centre without actually being in it, but isn't the nicest area. Heeley is fine, but is more family oriented than studenty. Stay far far away from Manor Top, Arbourthorne & Wybourn. These areas are all on the opposite side of the city centre from the uni, btw- still close, but not as direct as Walkley or Crookes.
S3- there are some flats north of the city centre that some students live in. Not especially convenient, IMO.
S6- Walkley and Hillsborough are both popular with people who study/work at the university. Fairly nice, reasonable rent. Easy access to the tram from Hillsborough. Close proximity to a huge Tesco and Morrisons. I used to live in Walkley while my husband was at the uni and can recommend it.
S7- Nether Edge- nice, can be expensive, not especially convenient for the uni but still pretty popular.
S10- Crookes and Broomhill aka student central. Most of the halls of residence are located around here so it's always crawling with students. Nice, though.
S11- Ecclesall Road & Hunters Bar- nice. expensive. Can't get cable (just DSL broadband and satellite TV.) Ecclesall Road is very busy, lots of nightlife around here.
That's it for the major areas near the uni- there are lots of other lovely neighbourhoods, but they're all farther out so I'm assuming you wouldn't be interested.