C25K, or Couch to 5k, is a running program to get folks from sitting on the couch to running a 5k (or 30 consecutive minutes) in just 9 weeks. C25K uses an alternating run/walk process. In week One, you run just 60 seconds at a time. By week Nine, you'll run 30 minutes at a time.
Keep in mind that even if this program is too aggressive for you, you can still work it. If you're not ready to move on to the next week, don't...just repeat the current week. Sure it'll take you longer than 9 weeks. But it's still going to happen much faster than if you stayed on the couch!
I am training to do a 5k the first weekend in July with a good friend. I've been running some, more than 60 seconds at a time. And this is the second time in a year that I've tackled running. So, the first week or so should come fairly easily. But perhaps that will give me the boost I need to stick with it for all 9 weeks and run that entire 5k in just under 3 months.