If you already think social networks give you a bit more information than you want about some people, TrueScoop's new Facebook application might make you cringe. It's completely free public records search, a service that lots of websites charge for, usually so potential employers can do background checks.
Google Noticeboard. It's a Firefox add-on can be used to create a message - including a voice recording and some text - which you can then send to other members, even if the other members doesn't installed Noticeboard you can still as audio as OGG email attachment.