I can’t remember where I first heard about this website, but I’m sure glad I found out about it. Tim Krabbé’s website Chess Curiosities is filled with great games, tactics, and studies. Krabbé keeps an open chess diary, and posts interesting notes about the evolving world of chess. The great thing about Krabbé’s site is that it offers a lot of free PGN downloads that work for both Mac and PC. If you haven’t seen his site before, I would highly recommend giving it a look!
You can find Chess Curiosities here: http://timkr.home.xs4all.nl/chess/chess.html