We have had a safe deposit box for many years at our local bank. The primary reason we have it is for an offsite location for my computer backup, though we also keep our passports, and some old photo negatives there. That's it. If something should happen to my computer or backup at home (fire, theft, tornado, etc.), I have the backup at the bank I can recover our important data from. Since they are on the other side of town in a different environment, it's unlikely they would suffer the same disaster scenario as us.
We currently pay about $60 per year for the safe deposit box. It started out around $20/yr and seems to creep up a bit more each year. It's getting to the point where it would be nice to find a cheaper alternative, but I haven't been comfortable with the friend/family option yet. I don't like leaving my stuff at someone else's house, and it would be awkward when I need to swap my backup drives. I generate too much data each day (videos, etc.) for online backups to be useful (too slow, too costly).
We also have a small "fire proof" file cabinet that I keep under my desk. For the most part it's just documents like wedding and birth certificates, wills, and that sort of thing. I have digital copies of most of these, but still try to protect the originals. I think it only has about a one hour rating, so I'm not sure how well it would hold up in a roaring forest fire, but it's better than nothing.
Otherwise, I try to digitize everything I can so I can have multiple backups for the worst case scenarios. We don't really own anything of significant value, such as jewelry, guns, or collectibles. Mostly just sentimental items that have more meaning than monetary value.
We had a break-in about 25-30 years ago and all they really took was a camera and my wife's jewelry. No significant monetary value, but it was sad to lose some of the sentimental jewelry items from our dating years. Ironically, we had several bags of items (CD's, electronics, etc.) in our living room in preparation for a garage sale and they didn't touch those at all.