Lots of people have disconnected their land lines and use their mobile phones exclusively.
However land lines still have a place in today's world, especially for people who talk on the phone a lot.
Mobile phones can cut in and out, but a land line (or Voice-over-IP line) will be more reliable, more clear, and a cordless phone can provide more talk time on a single battery than a mobile phone.
If you have a broadband Internet connection, check out these Voice-Over-IP devices.
OBi200 from Newegg or Amazon for $40.
Supports up to 4 voice-over-IP services on your single home/cordless phone system.
OBi202 from Newegg for $55.
Supports up to 4 voice-over-IP services on up to 2 home/cordless phone systems (a good way to use one phone for personal, and another phone for business, through the same box).
After you get the OBi device, register it on OBiTalk.com.
From that page, click "Approved Service Providers" to see a list of VoIP providers that OBi can quickly apply onto your account.
One of those services is PhonePower, and OBi currently has an offer to give you PhonePower for $35/yr.
The service includes a US or Canada phone number, free incoming calls, 300 outgoing minutes/month, call forwarding, call waiting, Caller ID with name, voicemail-to-email, E911, and fax.
They give you a real phone number, which you can also set your Google Voice account to ring (if you use Google Voice).
You can move your OBi device to any Internet connection, and your phone number will still work.
However be sure to tell customer service to update the address of your phone into the E911 system, so when someone dials 911 from your land line phone, the correct address will appear on the operator's screen.