I do some Abs with just about every workout but I don't really headline them since they usually only take me at the most about five minutes. I usually do them at the end of every workout. I mix it up by doing Crunches one day, and Leg Raises another. Some days I use the Total Gym to do my Abs or I may use a roller to do some floor stretch-outs. The point is to keep mixing it up and do a bit each day. Abs is one muscle group that you can do every day of the week if you want to.
So today I kept it simple and did some basic crunches - 100 in all and that was enough! But before I did a Leg Workout. Oh yah, I did another split workout day today, in the morning for my Cardio I hit the punching bag for 10 minutes - it's a great cardio workout if you keep busy.
Total workout time: About 1 hour done in my home gym.