RogerS: I'm using a 1 GB MMC memory card, too. I repartitioned it so there's a 64 MB VFAT partition (exactly the same size as the original MMC that ships with the Nokia 770) and allocated the rest of the card to an EXT3 partition (which also holds the swap file). With such a Linux partition, you'd hardly need the FAT partition, I only use it to hold the files needed to restore the Extended Root Filesystem after a reflash (xterm, my Root.sh script, etc.).

dr_kludge: If you use a swap file instead of a swap partition, trying different sizes is easy, you can simply recreate the swap file. Keep in mind, though, that there have been reports of sizes > 24 or 32 MB to crash the device. (Haven't tested that myself yet.)

msaunby: That's an interesting idea worth a try. It's like using a swap file instead of a swap partion, you're using an ext3 loopback mount instead of a partition. The scratchbox mount command could be stored on the MMC, too, so it's always available after a reflash.