However to get the balance right and not spend too much time on cardio, but to get the benefits that it provides, I have added some sprint intervals at the end of one or two weights sessions each week. So after 45 minutes of weights, I jog to the track or a field and run as fast as I can for 4-8 sets. The distance tends to be anywhere from 40-80 metres. My recovery tends to be a slow walk back. I'm not training for speed so I don't mind if I don't feel completely fresh before my next set.
The great thing about sprints is practically anyone can do them. You don't have to be fast. You just have to run at your top speed, whatever that is. I have felt much fitter and the whole session only takes between 15-20 minutes. This could be done as a workout on its own. Just make sure you warm up with some light jogging and then a few 75% sprints, gradually building your pace before starting your main sets.
Also, if you haven't run for a while or are new to running, try running fast for each set rather than sprining all out. This will allow you to build things up gradually.