I don't always find time for a defined workout, but I do a lot of gardening, so I try to make that into a mini workout, I do a lot of bending and lifting and stretching and try to maximize those movements to get a benefit. If one works at it you can really work up a sweat!
Lifting bags of mulch is a great muscle builder.
Pulling weeds gives a much needed tummy tightener if you bend just right and pull in those abdominals while doing it.
Even watering can become a great workout if you stretch and reach while holding the hose.