YouMail
While it may seem like not much can be done to improve your simple "leave a message," YouMail amps up voicemail with a number of features meant to take it to a whole new level. The free service allows you to do a number of things including accessing your voicemail online and by phone, having your messages sent to your email and the ability to save messages forever. Which is great, but not that cool, right? What is cool is that it allows different callers to hear different recordings. So for instance, if your mom calls she'll hear "I am busy working hard, making money and saving the world one day at a time," while your friend may hear, "Already at the bar. You owe me a round."
You can also choose a pre-made message provided by YouMail that can sound professional or fun like "Fingers are Fat." If someone calls that you have no interest in talking to like, ever (aka telemarketers, ex-girlfriends/boyfriends, your crazy uncle Fred from Appalachia), DitchMail plays them a message and then hangs up on them. The newest feature allows you to publish the messages people leave you via email, AIM, MSN, Yahoo Messenger, SKYPE, MySpace, Facebook, Twitter and Pownce which is great for work and a ton of other areas in life. However, it could be potentially hazardous to your reputation and could be used to make a strong case for thinking before dialing. If you don't, your booty call may just end up all over the net.