On days I really don't want to exercise, I tell myself, "I can do ANYTHING for 10 minutes." I try to do at least 10 minuts of cardio and at least 10 minutes of strength 5 days a week. This is a do-able amount of time for me.
I use Hemalayaa's Bollywood Dance DVD's for cardio. Most of them are already broken into 10-15 minute segments, so it's easy to do a quick workout and to switch it up so I don't get bored. for strength, I use the SparkPeople Firm & Fit DVD.