http://www.informationweek.com/news/storage/systems/showArticle.jhtml?articleID=225701006&subSection=NewsI've used GVoice since they opened up. It's the only number I give out to random people or post on craigslist when selling things. It ties all your cellphones, home phone, and whatever phones into one line. You choose a local number. If you have a palm webos, android, or blackberry phone you can download the GoogleVoice app. iphones, i think you're better off with the web app.
You can screen callers, forced them to say their names before you put them through or send them to voicemail. You can block the caller from calling again. If they do call again, they're hear a "this number has been disconnected or not in service" message. Free SMS messages. Back to voicemails, when people leave voicemails it gets transcribe to a text message that'll you'll get. It does a horrible job if they leave a message in hmong. Obviously!
http://www.google.com/voice to sign up.