Diet sodas are, more often than not, worse for you than regular sodas. One embalms you from the inside out, the other just overworks your pancreas. Possibly making you overweight.
If you're going to drink soda, drink a normal soda. If you want to get away from caffeine alone, get Sprite, Sierra Mist, or Squirt. They're caffeine free. Not sugar free, however.
Sodas, it seems, are about the worst contributor to some health problems people are facing these days with all the diabetes and obesity.

When I stopped drinking soda, I started buying a lot of tea and keeping it in my home. It does keep you sated so that you won't crave soda so much. It takes a lot of time and abstinence from soda to finally get you used to the lifestyle though. Keep in mind that tea does dehydrate you more than it hydrates you. Some studies show that, I guess.
Just be sure to drink some water every day.