Verizon (only carrier that works here on the Metro!). I've been with Verizon for 5 years. I have a contract, nationwide plan.
I bought my mom a phone last year for Mother's Day, and I pay for a SharePlan so we can keep in touch for free and she can have it while she travels by herself back in Ohio.
700 anytime minutes, unlimited nights and weekends for $69.99/month ($80 after taxes and all that other crap)
ETA: Originally got one when my dad was undergoing cancer treatments so I could be contacted in the event of any emergency. Now, it's my primary phone line. Most of my friends and some family have it, so we all talk for free. My mom is getting older and lives alone, and I like being able to check on her and get in touch with her anytime--and vice versa. Plus, I sometimes need it for work when I travel for the government.