There is 365chess.com. You can look up players and download all the games that they have in their database. I don't know if that database is as big as chessbase, though. To view the games you'd need software for that. If you don't have something, then you can download winboard for free. (In the resources link at top).
chess database resource to prepare against opponents

In order to prepare against opponents (and have a look which games and openings they have played), you will need a database in which the players' names are the same as here on the site to find them. For that, you will need to use the chess.com game database called game explorer (fully accessible for premium members).
Hi,
I would like to know which resouces use players here to prepare against their opponents.
I know there are the chessbase big-databases updated yearly but the chessbase software is quite expensive.
I only need a tool to get as much games of my opponents as possible.
For training I have chess.com ;-)