One easy fix is to simply change the switch plate and outlet covers. This can be anything from changing out yellowing off-white plates to white plates or converting all the covers to colored or nickel or bronze colored switch plate and outlet covers. Prices for these range from 26 cents to $32 for traditional outlet and switch plates.
Another easy change is painting. You can get mismixed paint for 50% off or more at home improvement stores, you just have to check. Colors of course are subject to availability, but you might be pleasantly surprised at what you can find.
Finally, move the furniture around in your living areas. Just changing the flow of the room and maybe adding certain new pictures can make the space feel as though you just completed a major remodel!