If you're anything like me you'll have a nightmare with online usernames and passwords. Some sites let you use your email address as your username, on others I end up being simonbenham679 (how are you supposed to ever remember that), still others like our bank give you a number as a username. Then you come on to the disaster which is passwords. My early approach was to have the same password for every site. Then I started using one more secure password for sites where I could lose money and another for sites where I didn't care, but then realised for the sites where I didn't think I cared (such as Twitter) I probably did care a lot if anyone every managed to log in as me and start posting malicious stuff. Then sites start insisting you have more complex passwords (one of the ones I have to use at BlueArc demands you have punctuation in your password).
Well my solution (for now at least until we can all use retina scans or something similar) is eWallet. At the most basic levels it's an app which stores all your online account details in a highly encrypted file, meaning you only need to remember one password to get into eWallet, which then gives you access to all your other passwords and usernames. That alone for me is a genius function.
Usefully it then stores that file online, so that you can access it from other devices, and if you lose your tablet or phone you don't lose any of the information.
But now I use it to store all sorts of other information I occasionally need. My passport and driving license details. My blood type. Bank account details and contact numbers. Anything I might need access to but which I don't really want in plain text which anyone can read - well to be honest I'm happy for everyone to know my blood type - A+ if you were interested :)
It also has a facility to suggest passwords which are secure, something I notice other devices are increasinly doing, which is helpful as long as you don't then have to remember them!
There are lots of other similar apps, this just happens to be the one I use. I'd be interested to know what other people do - perhaps your memory is just much better than mine.