Is there any software existing to manage all online accounts ? I have so many accounts, I can’t even remember most of them. If there is, can it manage multiple accounts on a single site ?
Netvibes doesn't support all account but only more generic ones like Facebook, Games etc.
KeePass is another option and it has a portable version that you can have on a flash drive which enables you to use it on any computer without relying on an online service.
I use 1password myself, LastPass is good too, but bear in mind it's an online service. 1password keeps everything on your local drive, and can still be synced across machines using a dropbox like service.