Jangl is an interesting service that allows you to make anonymous (unidentifiable) phone calls to anyone with an email address. Create an account, enter an email address, and you'll get a unique phone number for that address. You can now call that number and leave a voice message that will be forwarded along to the email address. This works with regular landlines, cell phones, or even VoIP systems. You preserve your anonymity, because when you call via that new number, the call will show as originating from within the Jangl network, so you don't have to worry about exposing yourself. Your message recipient is given a number—not your real number—to call back to reply to your message.
Jangl supports other services a well, including a web based text message platform. You can send and receive SMS text messages even if you—or your recipient—don't have a messaging-enabled cell phone.
A free service, Jangl works in over thirty countries in North- and Latin America, as well as the UK and much of Europe.