If you're tight on space, you can delete the sample movie and sample images. There are also user manuals in a zillion languages. You only need the languages you know, maybe not even that.

I formatted my SD cards with ext3 (i use linux on my desktop, and they're mountable there). This lets you run executables from the SD card. So, you can become root, move bits to an SD card, and use symlinks from the root FS to the SD card. Well, you can if you know how. xterm, gainroot, mke2fs, etc.