Password management software

I work for a medium sized organisation, around 100 users. We have an IT staff of 3 and a number of passwords in use. We don't keep user passwords, they change far too often and can be reset easily in the event we need access to an account.

In the event I get hit by a bus tomorrow, I am concerned about how to best keep important system passwords available for the organisation without compromising security.

If I give my tech staff top level admin passwords, it's not great practice. But if I only keep them to myself then that's a risky move for the organisation. I've therefore looked at both Password management software (online and locally installed) and simply keeping an encrypted excel spreadsheet with the passwords in. But then I've got to password protect that, and who gets that password.....!

Anyway, I'd be interested in how others have dealt with this issue? I've considered creating a package for MDs/Finance directors in the event they need this information. Sound feasible?