FAT partition is going to be most, if not all of the space of your card. depending on whether you plan to boot of from that card or not. If you plan to boot off from that card, then I'll say about 512MB-1GB should be devote to ext2 and the rest to FAT. I already used over 700MB on the card, w/ tons of app. That's why people buy large SD card. I bought mine 8GB SDHC for like $70, and it work flowlessly. Just a warning, you can't use SDHC card w/ the stock kernel, at least not yet anyway. The next upgrade will persumably support it, as people are already start using them