This section is under construction, but you can go to the team's official sites (you can buy tickets through them).
Canadiens (hockey) at the Molson Center just west of the Windsor train station (Bonaventure metro station). There's an official Canadiens fan club page. The season starts in late autumn and can continues until spring and early summer.
Alouettes (canadian football) at the Percival Molson stadium on the McGill university campus (they use to play at the Olympic stadium but they moved in 1998 to their new outdoor stadium). It's located at the corner of du Parc and des Pins ave. but you can take a bus shuttle from the corner of University and Ste-Catherine street west to the stadium (McGill metro station). The season starts in mid-summer (July) and ends in late autumn.
Impact (soccer) : they play at the new Saputo stadium www.stadesaputo.com ) next to the Olympic stadium (Viau metro station).
The Expos (national baseball league) do not play in Montreal anymore, the team has moved to Washington and is now named the Nationals