Firstly, it is excellent you are considering such things. Too few do. A little planning can make a big difference for those who you leave behind when you pass away.
The first thing to consider is to what extent the solution needs to be based on technology. Too often, people believe that because technology is involved, the solution must also be based in technology. In reality, most of the time, all you need is a pen and paper and a secure way to store the information you record in such a way that it cannot be accessed until after you pass away.
My recommendation would be to retain the services of a reputable legal firm. Apart from advising you on the key things to consider, most firms can also facilitate the storage of sensitive information. They can tell you what documentation is important, how to setup a trust or account which will provide your spouse with sufficient funds to live off until the estate is settled and what information, such as details on bank accounts, shares, insurance policies etc, will facilitate processing of the estate.
As mentioned by others, there is no need to record your bank account passwords or pin numbers. Once financial institutions know you are deceased, they will freeze your accounts until the estate is settled. What you want to do is ensure that sufficient documentation is available to process the estate as quickly as possible and if you can and if necessary, provide some source of funds your spouse can use until the estate is settled.
One area where on-line security storage solutions can be of use is for informatio which may change too frequentlly to be easily documented and left with your legal agent. This sort of information is rarely of high sensitivity or value - more convenience stuff. For example, access to some on-line accounts where there may be data your spouse would want to access, such a photos, possibly emails etc. In this case, these on-line services may be useful.
The key here is less the soltuion and more the act of thinking and planning. Keep things simple and straight-forward. Don't go for highly technical solutions, especially if your spouse isn't as technical as you. Go for solutions which will make life as easy for them and which has sufficient security for you and which are in-line with the valule/importance of the items being considered (usually, this means importance/relevance to your spouse, not necessarily to you).