Water features are one of the fastest growing areas of residential homeowner improvements -- the soothing sound of the water splashing over the boulders in a stream helps to cancel road noise and can even be a place for kids (and adults) to relax and play. Pondless waterfalls are recommended for families with small children; the design allows them to "walk on the water." Good stuff.
Water features are a homeowner-friendly landscaping idea and are easily placed in just about any spot. The most important factor to consider is to site the feature so that it can be enjoyed at close hand, at the edge of a patio, for example, or through a large viewing window. Don't build the thing at the back property line or only the critters will enjoy it.
Arbors and pergolas (large arbors) are another way to add an outdoor room to your home; they are typically constructed over a patio and can be planted such that they will provide shade in the hot summer. They can be built from scratch or ordered in kit form, an increasingly popular option.
You should be sure to consider the anchoring requirements when scratch-building an arbor or pergola -- the structure is, by default, top-heavy and can, if not properly secured, end up as a pile of spare parts instead of a great landscaping idea! Clearly, not a desirable end result.
Ground-level decks and porches are reasonably easy for the somewhat experienced homeowner/carpenter to build; those up in the air are likely best left to a professional, given the extra support requirements. No matter where their location, they are a good landscaping idea to increase your outdoor living space at a very reasonable cost. Most decks are constructed of cedar or pressure-treated pine; composite materials are also available.
Patios are typically constructed of concrete -- gray or colored and surface-stamped -- but their construction is not easy for a homeowner to undertake. On the other hand, paver patios are a great way for a homeowner to build a patio.. The necessary materials are generally available at your local outdoor-products store, they usually offer instructional classes in paver construction, and they will help you if you encounter difficulties. Take advantage of them.
So, a variety of landscaping ideas for you to consider; in their basic form, they are all pretty easy to build. Look around your neighbors' homes, steal some ideas from them (they'll be flattered) and get to work.