Putting sensitive documents online in places like gmail/hotmail etc can be risky because these systems have relatively low security. An encrypted disk is probably a safer location IMO.
I have copied my photos to an old USB hard disk and have left at a trusted relative’s house for safe keeping. Now these are not getting updated, but it does provide a base set of photos; this thread has reminded me that I was going to do an update !
It would be possible to setup a backup regime to automatically (or on demand) copy sensitive data to a trusted friend/relative’s computer using a VPN and an encrypted volume (like truecrypt), but you would need some IT skills to do this. Regardless, the frequency of backup should be matched to how much data you are prepared to lose !

I do use online storage for information which I consider is not sensitive eg: collection of manuals for various pieces of equipment which I own (at least before the fire!), some key family and friends contact details, medication details (including dosage), optical glasses script, medical history for everyone, contact details for banks, credit cards, house and car insurance (include and toll free numbers). I consider this is the basic info which I will need if the house is un reachable or when I’m travelling.

One possible enhancement for Eugene’s document binder could be to include a photocopy of your own AND everyone else’s documents in each person’s binder ?
If you need to you can use the copies to give to authorities and preserve the originals. It also has the benefit that if you become separated, you can still access all the info.

You could include a large size, clear, colour portrait of each person in your family (and copies), this may assist if you become separated and need to track someone down, you may consider some pictures of your extended family too ? Having a photo can be comforting too, especially if you become separated for any reason.