I use a buffalo linkstation. 300gb (it’s a few years old). You can attach with USB or just plug into your home network.
One caveat about these: they are not redundant (no RAID). If the drive in this fails, you’ll STILL lose everything that isn’t backed up somewhere else. Still, if you are using them to backup your laptop, it’s better than nothing.
I plan on getting a multidrive NAS RAID cabinet in the next few months to solve this issue.