Like everyone else said - clean and neat, uncluttered, and curb appeal.
I've seen many a generic house sell based solely on the impression the buyers got when we pulled into the drive. I've also seen many a great house passed over because they looked shabby/nasty/bad from the street.
Sounds like what you've done inside is the right things. Neutralized, de-clutter, paint (with good paint, properly taped and cleanly cut in), and a general de-fuzzing of all the rough edges.
Put on your "new person in the house" glasses and walk around. Any littley piddly problems you see will be seen as big honkin' problems by potential buyers. Pulled tape joints, corroded faucets, etc. You might spend a few hundred bucks on all new faucets and some toilet rebuild kits (flapper valve, float, handle, and tank seals and bolts). New faucets will get noticed, even though they sound like a trivial item. If you have a mechanical closet where the water heater and HVAC reside, grab your shop vac and a dust rag and have at it. Guys invariably look there, and it makes a profoundly positive impression if your HVAC clost is clean.
Replace all the air filters, too. Especially if you have filters in the returns. Nothing makes people turn up their nose like a fuzzy air filter. Makes them wonder what else hasn't been done.
Wipe down the cabinets inside/under all the sinks. Repaint under them if needed.
If you have exposed wood grab some lemon oil and do a general wipedown.
Clean all the windows. Then clean them again.
Replace or repair any missing/damaged window screens.
Wipe down, dust, wash, and otherwise clean all light fixtures. If you have any that are noticeably dated, run down to the local hardware store and get some inexpensive replacements.
Same for doorknobs and cabinet pulls.
If you have any cabinets that have been repainted and the hinges were painted over, get new ones to match the pulls. Painted hinges just look crappy. Unless you have desinger hinges in special sizes, you should be able to get generic hinges at the hardware store for under $2 each.
Brad