You don't have to be Catholic to celebrate Mardi Gras today, and you definitely don't need the excuse of Lent to give up a habit. CNET suggests giving up Facebook, and even has some guidelines for how to do it.
I don't know that I'd give up Facebook, as I'm not painfully addicted, and I certainly would not give up my Twitter, since I feel like I'm just getting started. What I could give up is using my cell phone in places it might not be appropriate, and trying not to have meaningful conversations over text messages.
What I definitely am too addicted to give up are my TiVo, whipping out my iPhone to solve all my problems, and playing video games to unwind. Some things are just non-negotiable.
So tell me, if you had to (or are going to), what technology would you/could you give up? What could you definitely not?