Pasta and a jar of sauce! I love Loyd Grossman's Smoky Bacon. Baked potatoes and various filling (I microwave mine until done, approx 8 mins for a medium one) then grill on both sides to crisp it up a bit. Cheese and beans or tuna, sweetcorn and mayo are favourites. Salad with tuna, chicken, ham, baked/boiled potatoes. Packet of stir fry and a packet of chinese sauce & noodles. Bolognaise (chop & fry an onion, brown 500g pack of mince, jar of sauce (I use Dolmio Original) plus a few chopped mushrooms, simmer for 20 mins, serve with spaghetti.
Ah well, that's just about exhausted my weekly menu! Shout if you want any more ideas! If it takes more than 20 mins, I'm not interested!