AFAIK, Toshiba is the only one that has confirmed having a 64GB chip.
Alright, here you go.
Samsung: http://www.iphonealley.com/current/samsung-announces-64gb-flash-chip-ready-for-market
SanDisk: http://www.sandisk.com/about-sandisk/press-room/press-releases/2010/2010-02-15-sandisk-doubles-storage-capacity-for-mobile-phones-and-portable-devices-with-introduction-of-64gb-inand-
To your credit, Toshiba was the first. Toshiba unveiled it in December, Samsung in January, and SanDisk in February