I predict that this is going to be a HOT new product from Google in the coming months.  Remember, you saw it here first! 
https://www.google.com/voice/about#How about getting a single phone number you can give out, that when called will ring on all your landlines and cell phones at once so you never miss a call, will have centralized voicemail you can access from anywhere via the web, (voicemails you can convert to text and print out) call waiting / screening (listen to a caller before answering the phone), call forwarding, conference calls, all the features.  Place calls anywhere in the US for free, send SMS/Text messages for free... All this at no cost.  Probably have to put up with some Adsense/Advertising on the web site.
Looks to be pretty United States-centric for the first go round, but I suspect will be widened to include Canada and Europe if it takes off..
Features:
    * Call screening - Announce and screen callers
    * Listen in - Listen before taking a call
    * Block calls - Keep unwanted callers at bay
    * SMS - Send, receive, and store SMS
    * Place calls - Call US numbers for free
    * Taking calls - Answer on any of your phones
    * Phone routing - Phones ring based on who calls
    * Forwarding phones - Add phones and decide which ring
    * Voicemail transcripts - Read what your voicemail says
    * Listen to voicemail - Check online or from your phone
    * Notifications - Receive voicemails via email or SMS
    * Personalize greeting - Vary greetings by caller
    * Share voicemail - Forward or download voicemails
    * Conference calling - Join people into a single call
    * Call record - Record calls and store them online
    * Call switch - Switch phones during a call
    * Mobile site - View your inbox from your mobile
    * GOOG-411 - Check directory assistance
    * Manage groups - Set preferences by group