James,
I use Sandisk Extreme III 2 GB and 4 GB cards primarily as well as the 2 GB version of the Lexar Professional card (133X). The Lexar is currently available through Adorama for $84.

I stick with Sandisk and Lexar because I've never had one fail (knock on the side of my head for even writing that) while I've had failures from other brands. Plus, the Extreme III cards seem to work really well with my Canons.

Happy shopping.

Jim