I work for three different employers, and two don't require me to go into an office at all. One does, a few hours per week. I do database maintenance, editing, writing, internet researching, and a bit of transcription.
I love working from home! There are perks, like being able to stay home with a sick child, having a freshly brewed pot of coffee to myself

, getting laundry done at the same time, and wearing super-comfy clothes, to name a few.
The biggest challenge for me is managing my time/week very carefully so that I meet all my deadlines. There is always some household chore that needs to be done, but I have to ignore it and get my "for-pay" stuff done first! Once in a while, I also have to keep the dd's quiet when I have an important phone call, which isn't always easy. Generally though, I get everything completed before I pick them up from school, or after they're in bed.
I've also sold on eBay, but that's more for fun than for funds.