Your first option is to follow the game live by using Live Gameday on MLB.com. You cannot see the actual game, but you can follow the pitch, its location, and where it went, etc. It is very detailed and free. You can even see the history of the innings so you can step out for a bit, come back and know what happened.
Here’s a link to a different type of scoring update: http://sports.yahoo.com/mlb/gamechannel?… That’s Yahoo’s, but some people complain that it’s a few batters behind.
You can also buy a subscription to MLB.com and watch them there. Another good one is http://watch-baseball-live.com/. Of course, they both cost money, but they’re worth it. Using MLB Premium TV (found at http://www.mlb.com/mlb/subscriptions/) you can watch all 2,430 MLB games for only $20 a month. You can also play back last games. You can get a free five day trial, though. There are also options to just get your favorite teams out of market games.
The third option is to try a free site (note that these don’t work, freeze up, and will make your computer much, much slower with uncountable viruses). One site would be http://watching-free.blogspot.com/.
Another option is using http://www.freebaseballradio.com/. You can listen to the games, but not watch them.
Lastly, consider tv services like Sling, or buy an over the air antenna to get network broadcast games.