Here's what I did with my 2GB card.
The first partition is 256MB FAT32. I store my e-books and such here. This partition gets unmounted from the 770 and mounted on your PC when you connect with the USB cable.
The second partition is 1.6GB ext2. Here is where my maemo-mapper maps are stored along with a few videos and such.
The remaining 128MB or so is formated as linux swap.

Now, in order to use this setup, you need to edit a few files as root so make sure you can become root and get a # prompt. Also you'll need an editor that you know how to use. I like the built-in vi editor or the vim application but I've been using vi for 20 years. It's not the easiest editor to learn. Midnight Commander (mc) is a cool console file manager that has an editor and I think there's a leafpad for OS2006.

The first thing we'll do is tell the 770 how to mount the partitions by adding a few lines to /etc/fstab. Open xterm (or ssh in from your PC) and "switch user" (su) to root by typing
note the space and dash after su.
Your prompt should end in ~# If not, you're not root. fix this before continuing.

Open /etc/fstab in your editor of choice and add the folowing 2 lines:
Next we want to load the ext2 kernel module and mount the ext2 partition and activate the swap partition. Open /etc/init.d/minircS in your editor. near the top, right after the PATH= line add this line:
Then at the end of the file, just before the exit 0 line, add:
Now to be nice, we want to unmount mmc2 and de-activate the swap when re-booting or shutting down so edit both /etc/init.d/minireboot and /etc/init.d/minishutdown. Find the line that starts: umount -r and add /media/mmc2 to that line and add swapoff -a so it looks like this:
reboot and that's it. You now have a 128MB swap, a big FAT32 partition at /media/mmc1 and a nice big ext2 partition at /media/mmc2.