I just bought three 8 GB Sandisk Extreme III CF cards for $90 from B&H (no shipping because I am a NAPP member) and it comes with a $70 rebate so 24 GB for $20!
The following cards are on sale at Adorama and Amazon. Not only are these prices phenomenal, the shipping is free too! Prices are good only until November 30th).
8 GB Cards:
Adorama SanDisk 8 GB Extreme III Compact Flash Memory Card $29.95
4 GB Cards SanDisk 4 GB Extreme III Compact Flash Memory Card $19.95