I know at buy.com you can pick up a 2gig SD card for $5.99 with free shipping...
damn good deal!
If you put HBC/Zelda hacked save, and FTPii, you'll never have to take the SD card back out of your Wii... you can FTPii your files from your PC to your Wii (which I do, since I only have a camera for an SD reader!)