BathroomNumber one on the list? A mid-range bathroom improvement. Typically you can expect to more than get more money back by sprucing up the bathroom. Note the emphasis on "mid-range": putting a bunch of high-end improvements is likely to cost you more than you'll get back when it's time to sell.
Re-SidingAnother idea is re-siding your house. Curb appeal is everything when you go to sell your home, as it's the first thing potential buyers will see, both in person and through pictures, and if your old siding is looking worn-out it will definitely affect how much buyers are willing to pay for your home. You can go traditional, or you can invest in log home siding, which will make your home look great and appealing to a wider range of buyers.
KitchenRounding out the list is a minor kitchen remodeling. Refacing cabinets can be a much more cost-effective way to add some zing to your kitchen than replacing them, and putting down a little better flooring can return more on your dollar than top-end coverings.
That being said, you're the one who knows your home the best. Maybe none of these make sense for you because you're already happy with the way your kitchen, bathroom and siding (if you have any) look. If you're looking to stay in your home, then convenience and your personal desires are more important than resale value. But if you're looking to sell, make sure you're not throwing away money doing remodeling that isn't going to pay for itself.