I recently had to help a family recover data from a deceased friend. They had no idea where to start, and I thought I might share the experience with others in case they might also have the same problem. With all of the places people visit and access every day, (electronic banking, email, facebook, online documents, tax data) it may seem daunting at first, but it turns out that with a little work on two passwords, you can get into most areas quite easily. Let's break this down into three steps:
Step 1: Gaining Local Access.
Most users are going to have been using a Windows-based machine. These machines generally require a user to "log in" to a computer. As long as the hard drive is not encrypted, gaining access to the data on the hard disk of a computer is as simple as using ANOTHER computer to treat that disk like a secondary drive (like it would treat a USB key or a CD-ROM). One way to achieve this is to remove the hard disk and place it into a computer with which you DO have access. Another way is to use a boot disk of some kind to load a different Operating System and treat the hard disk in the computer like it is the "other" disk. What's nice about the latter solution is that you don't need to take the computer apart at all.
Probably the easiest way to do this in Windows is to use a Windows Password Reset Disk.
Step 2: Gain Access To Email
The next step is to gain access to your loved ones email account. For this, you may need to contact the company that provides email access to your loved one.
If the loved one used an ISP email account (such as @cox.net, @comcast.net, or @att.net, etc), gaining access is as easy as calling up and pretending to be your loved one who has forgotten his/her address. They will provide you with a new temporary one. Be sure to have the billing address, social security number, phone number, and mother's maiden name available. Do not tell the ISP that your loved one is deceased because they will likely ask for a certificate of death to be faxed to them. But, those are not usually immediately available from the state (this may depend on the state), and you probably will need access to email much sooner than that.
If the loved one used a web mail account such as Yahoo Mail, Gmail, Hotmail, AOL Mail, etc, you can generally run through the "I forgot my password" routine. Hopefully you are asked questions you know the answer to.
If you were lucky enough to find that the passwords have been automatically filled in for you by the web browser, it doesn't mean you are home free. If anything was to happen to those saved passwords, you'd be locked out. The easiest solution is to use the forwarding options in the "mail filters" for that account to forward all of your loved ones email to an address you control so that you can log into that account from other computers. Go through the existing mail, and forward important stuff to yourself.
Step 3: Everything Else
Once you have access to you loved one's email account, you should be able to use that to bootstrap into all of the other accounts and services that your loved one used. Each of them should have an "I forgot my password" like near where you log in, and each of them will use email to send a new password to you from which you can log in.