People like to ask me which home improvements will add the most value to their homes. Generally, the rule is that the kitchen and master bathroom usually benefit the most from improvements. The official Realtor Magazine Cost vs. Value report has many more details regarding which improvements make the most sense in which areas. This PDF file is hard to read on screen, but if you print it, you can find out exactly how each specific improvement effects the values of home in specific areas of the country.
I think that if you are planning on moving, it is a good idea to spend your money on repairs and any possible maintenece issues before tackling big improvement projects. If you have more to spend, then get into bigger improvements like appliance upgrades, new fixtures, new flooring, etc. If you are not planning a move for a few years, but are interested in just making your home right for you, then I say ignore resale issues and do what you want. If you do something really horrible, there is plenty of time to change it, so do what you like, not what is popular!