This is not quite under $100 but close.
OCZ (OCZSSD2-2VTXE60G) Vertex 2 Extended SATA II 2.5" 60GB Solid State Drive, Read: 285MB/s, Write: 275MB/s | Canada Computers
I bought a 64GB Kingston SDnow V series for one of my books and was disappointed with the performance. I'm replacing it with a Vertex2.