I took the path less traveled and installed Ubuntu on my CR-48. Mostly this is a completely standard install, minus it using ChromeOS's kernel (for drivers) but the main drawback is the 8GB SSD-- it became full rather quickly. At present I'm looking at 320MB free on the drive.
I purchased a 16GB SD card and mounted it for DATA access and was able to offload some files to it, but it's highly under-utilized at the moment. I'm going to modify the boot configuration and mount some other directories there. Because it's flash memory, I'm thinking that good candidates are files that are written once and then read many times. I don't mind slow loading times so much, but I want to avoid completely stalling my system while I'm at it.
I want to move /home to the external drive out of convenience-- I figure what configuration files are loaded don't need to be super speedy for performance reasons, and I want to be able to throw stuff in Downloads safely. Is it safe to move /bin, or other things like /var and /etc? The external drive is much slower than the SSD, but Linux also has some of the best RAM caching algorithms I've ever seen. I do know I want to keep /opt on the SSD, as that's where the Chrome cache seems to end up, so I want that to be as fast as possible.
I guess that's a lot of buildup: my question is, which / directories in ubuntu linux need to be fast, and which directories can be moved to a slower drive without significantly impacting performance?