Here's an idea I love, which I originally saw at Clover Lane: Get yourself a nice, fresh notebook. Or download this free .PDF, print out the pages, punch holes in them, and stick them in a binder. Then:
1. Pick a room and either choose the appropriate printable page for it, or write the name down on the first page of your notebook. Then walk into that room and inspect it. Write down down everything that needs attention. You can include simple cleaning chores (like wash the ceiling and scrubbing the floorboards) to repairs (like fixing the grout or painting). If you like, you can also include things you'd like to change about the room (like change the color scheme or buy a couch slipcover).
2. Walk into the next room, change pages, and make notes.
3. Repeat until you've covered the whole house.
Now you have a handy checklist. You don't have to try to remember everything that needs doing, and you can systematically clean things up or make repairs.
So simple, but so effective, too!