I second starting Body Pump. It's fantastic for increasing your indurance. You'll probably find strength increases at first as well. Do you have a gym near you?

And Socks, there is nothing wrong with a rest day, infact you shouldn't do two hard training sessions in a row. Listen to your body, if it is telling you to rest then rest. It's better to do a great workout every other day then to do a half arsed one every day