GoBase
GoBase is a website by Jan van der Steen that contains a large collection of professional games, as well as a number of articles, including study material.
It has a database search engine for searching through the collection and includes an online replayer that can display the games found in the database.
A large part of GoBase, including the replayer, requires an username and password to access. Registration for the username and password was free. As of 5 August 2007, there is a 20€ fee in order to register an account. Registration must be done from a non-anonymous and non-free email account, failing which extra credentials must be supplied.
Anonymous: GoBase.org is not prompt at rectifying or explaining login errors, although your 20 euro "donation" will be cashed immediately.
Gobase has an RSS feed available. If you use LiveJournal, you can add
the gobase feed to your friends list.