No more fixed landline phones

I just got rid of my land-line phone and am now 100% cell phone dependent and I use SKYPE as my backup. This will becoming more and more popular. Hard to believe that about 10% of all internet users only use cell phones. Does anyone know different options for turning your PC or MAC into a telephone hub where you can have calls forwarded, have voice mail, etc. Kind of like SKYPE but for adults : )