Samsung has announced a 120 GB 1.8" Hard Drive, suitable for use in Apple's full-sized iPods. Currently, Apple's high-end iPod features an 80 GB drive.
Seagate also offers a 120 GB 1.8" Hard Drive, and Toshiba currently maxes out at 100 GB in the 1.8" variety.
Some recent rumors have indicated that Apple may be toying with the idea of going to an all-flash based lineup, however such a move would make high-capacity iPods impossible at a reasonable price point, even despite plummeting flash prices.