I'm about to buy the Canon S5is camera. I also plan to shoot movies with it and I'd need a large capacity memory card. But, I don't know what's the biggest memory
card that this camera can take.
mypoppy - My understanding is that you can go to at least 8MB but there are risks and considerations when you do. Personally, I have 5- 4GB chips and 6-2GB chips of various speeds, and that is the real issue, over size. I use the 4GB chips for shooting movies (primarily) as it gives me about a half hour of constant shooting (with an AC adapter).
The faster chips (Lexar 4GB Pro) shoot faster still shots than the Transcends, but then they should - the Lexar's are rated at Class 6 - 133X where the Transcends are class 6 but not rated for their speed. Shooting movies though, I cannot see the difference (except in the wallet).
A comment about the high density chips though. The larger the chip capacity, the larger the fall if something goes wrong (goes wrong - goes wrong).... A chip can get static zapped, shorted out, have bad mem location, etc., My Lexars are expensive but backed up by Lexar should something go wrong.... Not so with the Transcends, but then I didn't pay for that either. If I intend to shoot continuous shots, I use my Lexars; they are faster writing to the chip and ready for another shot much faster than the Transcends. Here you can really see the difference.
There was a comment made about CHDK and I agree completely. Above 4GB, you must partition (make it look like two chips/drives) if you intend to use it with CHDK.
I guess when it comes down to it, it depends on what you can afford and what you want to use if for. Short 'films' that I have shot with my class 6 Transcends look exactly the same as those shot with my class 6 - 133X Lexar Pro... and if one dies (or gets killed) it is not a big hit on the wallet.