Sometimes I cut up on strength exercises for a while and do cardio only 2 times a week and not for very long. I get back into the training cycle by watching fitness videos and doing the exercises given there. I set up a schedule (one or two videos per day, different each day) and try to follow it at least 2 weeks. After this, I feel motivated enough to continue without them, or if I really like them, I use them as well.
Sparkpeople's fitness videos with coach Nicole are good start, but Youtube offers other interesting stuff, too.