You need to find a Mother's Morning Out program or a babysitter to come to the house a couple times a week. It is unreasonable to expect a 3 and a 1 year old to leave you alone long enough to do anything other than go to the bathroom.
It may also be time to start thinking about TV. You'd be amazed what you can get done in 30 minutes. There are some decent, high-quality DVDs and OnDemand (if you have Comcast) programs. I particularly like the Baby Signing Time/Signing Time series (teaches sign language), Little Einsteins (not Baby Einsteins), and Zaboomafoo. Certainly, your son is old enough for Sesame Street.
Here's a tip someone told me that I have found works really, really well to get my son to be willing to play more independently when I need him to: Twice a day, stop all the other stuff I'm doing and get down on the floor and play with him (here's the hard part) with my UNDIVIDED attention for 30 minutes. If I do that, he's happy the rest of the day to play with my, er, divided attention. :-) Really does make a difference. One of the hardest things about staying at home for me is that because I spend such a quantity of time with my son, sometimes the quality of the time suffers. Got to find that balance. If you spend some good, quality time with them and then carve out (with outside help) some time for you, I think your life will be much improved! :-)