For those of you who's ordered the new Rebel XSi and need a memory card:
There is now a 16 GB SDHC card - and it only costs $64 @ Amazon. Amazing. If you're shooting JPEG at the highest quality on a Rebel XSi, this card can hold approximately 4571 photos. If you're shooting RAW the card can hold about 1290 photos. The 16 GB card is especially nice for long vacations; since you have capacity for 4571 photos on the memory card, you can avoid bringing a notebook computer to download your photos off the camera. $64 each @ Amazon:
Adata 16GB Turbo High Capacity Secure Digital SDHC Class 6 Memory Card
If you don't want the 16 GB card, here is an 8 GB SD card at Amazon for $30. This card can hold approximately 2285 JPEG or 645 RAW:
Transcend 8GB SDHC Card
These are not your 'big name brand cards', but I've always bought flash memory cards based 100% on price (Kingston, Viking, Transcend, 'no-name' brands) and they've all worked fine.
These are SDHC flash memory cards and they will ONLY work in the Rebel XSi (and 1DS Mark III & 1D Mark III.) They WILL NOT work in the Rebel, Rebel XT, Rebel XTi, 10D, 20D, 30D, 40D, 5D.
Given you can now buy 16 GB SDHC cards for $64, I wouldn't be surprised to see Canon switch all new Rebel XX0D models and X0D models to SD/SDHC.