Ah, then it sounds like the Excel file idea will work well. If the students will be creating their own passwords, one thing though that you need to make sure they understand is that the passwords they provide are not secure on your computer. Sometimes people will use the same password for everything and it would be A Bad Thing if one of your students would use the same password for your system as they do for accessing their bank account information online!
As a side note it is amazing what people will do sometimes without thinking: I was once working for a company that makes inkjet printers. When people call technical support with printing problems they are sometimes asked to send in a print sample along with the printheads they are using. One time I was going through new packages that we had received from customers and found a package where the "print sample" the guy had sent was his bank statement, complete with name, address, social security number, account numbers - the works! And to top it off from the information that was there it appears that the guy was a lawyer to boot! Needless to say I personally walked the papers down to the shredder...
Mike...