I have four:
My 'regular' blueyonder account, which contains my real name.
A second blueyonder account which does not contain my real name that I use to register on forums such as this. This enables me to respond to yellow envelope messages without revealing my identity.
A Hotmail account that I use to collect spam and also some newsletters. The main reason for having this is to have a web-based mail if Outlook, Outlook Express, or more likely the blueyonder mail servers, decide to play up.
A Gmail account - I got this purely out of curiosity and now its only use is for sending invites to others (only on request, I hasten to add).
I also have a business e-mail address and an e-mail account with a major customer, for when I work from their offices.