1. Paint kitchen cabinets.
2. Update cabinet handles.
3. Add extra seating areas outside.
4. Get new outlet and lightswitch plates.
These get super dirty with use, but are really cheap to replace (<$1 each). If you want to go really ~fancy~, paint your plates the same color as the wall so they disappear more.
5. Add molding.
6. Bump up the curb appeal.
The front of your house is the first thing potential buyers see, so make sure it's stately and welcoming. Add some extra plants to the porch or the entryway, paint the door.
Check out these other DIY tips for increasing your curb appeal here.
7. Make upgrades to your landscaping.
8. Turn any room into a bedroom with a closet or wardrobe.
9. Get rid of the popcorn ceiling.
Just make sure to get it tested for asbestos before you try this one yourself—some homes built before the 1970's have it in the ceiling. See how to do it here.