alias realias='$EDITOR ~/.aliases; source ~/.aliases'
I just came up with another one. This one should go into your crontab:
0 * * * * /usr/bin/crontab -l > ~/.latest_crontab
Every hour, on the hour, it copies your crontab into a local directory.
I just reinstalled Ubuntu, hoping that this fixed the problem that occurred after the Jackalope->Koala upgrade. It didn't, but I lost some stuff, including my crontab. I have a separate partition for /home, so I didn't lose everything in the reinstall, but crontabs are not stored in your local dir and thus are wiped.
And, thank you Damian Conway and chromatic for the realias thing!