So, how attached (excuse the pun) are you to the data on the attached memory card? If you can wipe it clean and start over, or even if you can take a backup first and start over, I'd recommend installing LVM. I know, from looking around Google-land, that LVM is available for Ubuntu (and has been since 7.04, if not before) but having never used LVM on Ubuntu I can't tell you if it's an option on initial install as it is with Fedora/Red Hat. If you can get it straight from the Live CD, that would be best, as configuring LVM after the fact is a bit of a pain on the root filesystem.

Using LVM, you can span filesystems over the internal HD and the memory card, or any other drives for that matter. One caveat: If you remove or otherwise lose the memory card after spanning the root filesystem, your system will not boot. I'd strongly recommend backups after doing this; a backup before doing it wouldn't hurt, either.