There are a couple of usefull web services that I want to share with you.
http://www.spamgourmet.com. Create disposable email addresses on the fly. You only have to create an account once on the Spamgourmet website, and from then on you can create disposable email addresses whenever needed. E.g. when you have to register on a website and are required to give your email address for a confirmation mail, you can at that moment think of and fill in a new email address. The confirmation email that is sent to your spamgourmet account will then be forwarded to your real account. The sender never sees your real address and after a ceirtain number of emails (that you specify), further undesirable email (spam) from that sender will be blocked.
http://www.mailinator.com. Create disposable email addresses on the fly. You can read the emails on the Mailinator website, no mail is forwarded to your real account. Your temporary email account will be automatically deleted after a few hours. It usage is similar to Spamgourmet, except that you do not have to register. The difference is also that anyone who can guess your temporary email address is able to read it (no passwords) and that mail is deleted after a few hours, whereas Spamgourmet forwards it to your real mail account.
http://www.yousendit.com. Share large (up to 1GB) files with other people. No passwords to share, no software to install, no accounts to create, and no full mailboxes. Your file is uploaded to their website and the recipient gets an email address with the obfuscated link where he/she can dowload your file.