Do not forget Digital Dungeon, Banana Republic and Gangsta's Paradise (follows Commodore Wire descriptions):
• Elysium's Banana Republic is another massive collection - I'd estimate it holds around 4500 titles! One interesting thing about the BR that I've noticed is the large proportion of T64 files to be found here...
• The Digital Dungeon is another great source of classic C64 games, divided into two sections - the main archive and the new archive. This "new" section contains a number of games that have only recently been cracked (generally speaking, the newer the crack, the better - more cheat options, docs, etc). The games you'll find in there are the best versions around, guaranteed! Between the two sections, the Digital Dungeon totals 3200 games.
• The games archive offered at Gangsta's Paradise contains some newer, less well known titles as well as several classics, with the quantity reaching 2500 in total. (down due a hd crash)
(Digital Dungeon mirror)
For more links, check Commodore Wire, they have a nice list: