Ask Slashdot: Simple Backups To a Neighbor?
I've been a happy user of buddybackup (.com) for years. It backs up to multiple friends computers and vice-versa (and a local copy). Pretty much runs in the background without any intrusiveness or adware.
No mac version though.
NASA Space Habitat Research Goes Undersea
Adult Swim even showed an animated version of what would happen called SeaLab 2021. Doesn't turn out too good for the crew most of the time.
What Free Antivirus Do You Install On Windows?
Another good option I haven't seen mentioned is PC Tools Spyware Doctor Starter Edition. You can get it free when you download Google Pack essentials.
The only problem I've had with it was when running simultaneously with Avira. The Avira scanner would freeze randomly while scanning until I shutdown Spyware Doctor.