I'd be careful with Crossfit if you're not in great shape. Seemingly A LOT of people get Rhabdomyolysis from Crossfit, which is breakdown of muscle cells into the bloodstream. That shit can actually kill you, not to mention set you months back in muscle strength. Read this blogpost:fitfeat.com/blog/2011/06/03/rhabdomyolysis-if-you-exercise-read-this/ and notice that 90% of the people writing there had done a Crossfit workout, particularly those with a lot of pushups/pullups and excentric excercise.
I don't doubt that at all. I 've been doing cf almost 2 years now but was in pretty decent shape before I started...
That site I mentioned has "WODs" for at home... might need 20 or 30lbs dumbbells for a couple of them, but other than that they're all do-able at home. You can also scale them as much as you need... I was just providing it at as a source for someone looking for some challenging workouts they can do at home :cool2:
Whatever you do, know your limits... better off stopping a work out early then pushing for that extra round or rep and getting hurt!