How about jumping rope? Cheap and super effective - plus hits your cardio sweet spot
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Otherwise, maybe consider checking out some exercise DVDs from your local library. Mine carries all kinds - that way you can test drive them before you decide to invest (or never bother to purchase, just rent different ones each week to keep it fresh!).
I have also been known to just create my own circuit training set - mix of cardio (jumping jacks, hikers, jogging, whatever floats your boat) and strength training. You could easily create your own 30 minute set + 5 for warm up & 5 for cool down.
For me, the key is to mix it up. I have used the "no excuses" line on myself 5-6 days a week since April. It is TOUGH because I also do not love it (and it requires 4:50am-5:15am wake up calls), but I love the way I feel when I'm done and I'm lovin' the rockin' results.