One 2-star hotel that I tested and that is good quality (budget: about 80 EUR/night for a double room). It is located in the nice area of Porta Romana, close to the Duomo by bus, or 3 stations away if you take the metro at Porta Romana or San Babila. The area is quiet and nice residential.

22 Marzo
Piazza Santa maria del Suffragio 3
Milano
Tel: +39 02-7010.7064
Metro: porta Romana

Very clean and simple with good value for money (even air conditionning). [Very] large double bedroom, nice chatty staff that advised to go to the second hotel the day they were full. In addition the use of the Internet point seems free of charge if you stay at the hotel :-) I strongly recommend.

I went also to a second hotel, 3 stars, a little bit more expansive but in the same area. Nice but very small rooms in comparison to the other one... and the staff, not that friendly, wanted me to pay up front which I refused! So better stick with the one above if you can.

Cinque Giornate
Piazza Cinque Giornate 6
Milano 20129
Tel: +39 02-546.3.433
Metro: porta Romana