The Province of Milan (www.visitamilano.it) has a Tourist Information office at Piazza Castello 1, right in front of the Sforzesco castle, telephone 0277404343, e-mail iat.info@provincia.milano.it. There also is a manned "Info Box" inside the central train station, in front of platforms 13/14.
Opening times (for both offices): Monday to Friday 09.00 - 18.00; Saturday 09.00-13.30 and 14.00 - 18.00; Sunday and holidays: 09.00-13.30 and 14.00 - 17.00. Closed on December 25th, January 1st, and May 1st.
There you can find free maps and small city guidebooks, leaflets on several cultural sites and events; you can also book guided tours of Milan and surroundings (lakes, shopping malls) and find information about hotels and residences.