I have been a single parent for many years and although still have some times when I find it hard I am generally pretty organised. I do most of the things above along these lines:
Do everything in bulk - EVERYTHING:
Food shopping: buy everything on special offer that is not perishable and some things can be frozen - I have practically a life time supply of baked beans, chopped tomatoes, loo roll, Weetabix, pasta, kids yogurts (the tube or sachet kind - buy when on offer for £1 and keep in freezer - take one out each day for packed lunch acts like a wee ice block)
Clothes shopping: Buy next size up in clothes so you always have stuff for them to grow into. I can get a bit carried away but buy stuff in sales such as cords, shirts, school uniform, shoes etc. I also buy myself pretty much the same clothes again and again as I know fits me so just buy more dresses in different colour.
Cooking: make double or triple of recipes and freeze the rest so you always have something for tea. I do soup in individual portions for my lunches at work, pasta sauce, chilli, lasagne etc. Any perishables you buy in bulk can be split into portions and frozen - I do this with things like sausages, chicken kiev, chicken breasts (I pre chop into portions so can just defrost then cook).
Packed lunches: on a sunday sort out the week's lunches, I pre-make sandwiches (I used to freeze them in bulk but have not done so lately), do wee pots of raisins, fruit, play time snacks etc all laid out.
Washing: I do it all at the weekend. I avoid washing DS's uniform items unless it is essential - I try to wipe him down with a damp cloth where possible. I make sure that he has tons of pants and socks and enough school uniform (bought in bulk in the sales - sainsburys and M&S have great uniform sales so I just buy stuff whenever I see a bargain).
Presents: always have a gift cupboard of items for your children and their friends - I buy books from book people, when I see toys such as lego on offer I buy a couple, shamelessly put items given to DS straight into the gift cupboard...... I also have some items for adults such as stationery, jewellery etc just buy stuff in sales again. Plus always have a selection of birthday cards and gift wrap on hand.
When a child gets an invitation to a party: ask child if they want to go, if yes reply to say they would love to come, at that point go to gift cupboard/card selection and wrap suitable gift/persuade child to scrawl in card. Stick card on gift and leave in prominent position. Add party time date location to calendar / electronic diary.
Toilettries: buy in bulk when on offer so you always have soap, deodorant, shampoo, painkillers, tampax etc. Sometimes I worry when I look in my bathroom cabinet and see six boxes of ibruprophen and five bottles of calpol but in an emergency at least we would be ok : )
Wine: buy by the case and always keep a bottle in the fridge.
Chocolate: always have some in the house.
A couple more tips:
Don't iron anything. Ever.
Use baby wipes for house work. I use them on the floor, to dust, to sponge marks off clothes etc etc. You can never have too many baby wipes (even if your child is no longer a baby)
Register with your local pharmacy for the minor ailments - this means that the pharmacist can prescribe medicine for things such as head lice, thread worms, veruccas, allergies etc. The pharmacist in my local chemist is lovely and we seem to end up in there every few weeks so she knows us well..... saves on having to make a GP appointment for those little things that children pick up on a regular basis.....
I work full time and find the best way to be organised in the morning is to get DS up and sitting with his breakfast and school clothes laid out while I shower, on a good day he will eat his breakfast and get dressed before I am out the shower : )