Sony announces details about the Sony Playstation Network dubbed online service for the Sony PS3 and other Sony consoles.

The Sony Playstation Network will be free of charge for the basic features offered.
Sony features the XMB™ (Xross Media Bar) user interface known from the PSP also on the Playstation Network navigation.
The feature-set of the Playstation Network looks very comprehensive featuring Web browser, voice chat, video chat, download game content, store/view photos and videos, download and listen to music and shop online.

If all that works, the Sony Playstation network can compete with the Xbox Live service.
Through the online PLAYSTATION Store, you can get stuff like game demos, game-related content and downloadable casual games, including titles developed by Sony Computer Entertainment World Wide Studios exclusively for download and play only on PS3, such as Blast Factor.

Your Playstation profile will include an electronic wallet functionality. How this wallet is filled is not specified yet.
More details in this Sony press-release.